Touch sensor, display device, display module, and electronic device

ABSTRACT

Sensing time of a touch sensor is shortened to increase responsiveness of touch sensing. A display device includes a gate driver, a plurality of touch sensors, and a plurality of touch wirings. The gate driver has a function of supplying a scan signal to the plurality of touch wirings at the same timing, and the touch sensors in different positions sense a plurality of touches at the same timing. In this manner, the responsiveness of touch sensing is increased. The gate driver has a function of controlling a scan signal for refreshing display and a scan signal used by the touch sensor for sensing.

TECHNICAL FIELD

One embodiment of the present invention relates to a touch sensor, adisplay device, a display module, and an electronic device.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. The present inventionrelates to a process, a machine, manufacture, or a composition ofmatter. In particular, one embodiment of the present invention relatesto a semiconductor device, a display device, a light-emitting device, apower storage device, a memory device, a touch panel, a driving methodthereof, and a manufacturing method thereof.

In this specification and the like, a semiconductor device refers to anelement, a circuit, a device, or the like that can function by utilizingsemiconductor characteristics. An example of the semiconductor device isa semiconductor element such as a transistor or a diode. Another exampleof the semiconductor device is a circuit including a semiconductorelement. Another example of the semiconductor device is a deviceprovided with a circuit including a semiconductor element.

BACKGROUND ART

Mobile devices such as smartphones, tablets, and electronic books havebecome increasingly popular. A reduced size, a reduced thickness, areduced weight, flexibility, or operability is demanded of electronicdevices. The electronic devices need to display images suitable for thebrightness of a use environment (i.e., an outdoor environment or anindoor environment). In addition, increased operability in touch inputis demanded of smartphones, tablets, e-book readers, and the like.

For example, a display device proposed in Patent Document 1 displays animage by utilizing reflected light in sufficiently bright externallight, such as natural light or light from an indoor lighting device,and displays an image by utilizing a light-transmitting element in anenvironment without enough brightness, thereby achieving low powerconsumption.

For example, in Patent Document 2, display in a certain region isselectively refreshed with the use of a decoder circuit to reduce powerconsumption of mobile devices.

For example, Patent Document 3 discloses hybrid display devices in eachof which a pixel circuit for controlling a liquid crystal element and apixel circuit for controlling a light-emitting element are provided inone pixel.

REFERENCE

-   [Patent Document 1] Japanese Published Patent Application No.    2011-154357-   [Patent Document 2] Japanese Published Patent Application No.    2011-085918-   [Patent Document 3] PCT International Publication No. WO2007/041150

DISCLOSURE OF INVENTION

One way to increase the operability of an electronic device at the timeof touch input is to increase the touch sensing frequency. However, whenthe touch sensing frequency is increased, a driving signal of a displaydevice or the like causes noise and the touch sensing accuracy isreduced.

A reduced size, a reduced thickness, a reduced weight, flexibility, oroperability is demanded of electronic devices. For higher operability,display devices including touch sensors are demanded. For a reducedsize, a reduced thickness, and a reduced weight, a reduction in thenumber of components is demanded. For flexibility, a reduction in thethickness of the display device is demand.

Smartphones, tablets, e-book readers, personal computers, and the likeare more and more often used in a place with bright external light.Among such mobile devices, smartphones, tablets, and the like which areoften used in a place with bright external light display an image with ahigh luminance to improve the viewability. These mobile devices thuseasily consume power. Accordingly, a large-capacity battery is necessaryfor long-term use. However, a higher-capacity battery leads to a heaviermobile device.

When used for a long time, smartphones, tablets, e-book readers, and thelike need to save power. To control power consumption, typically, powergating, clock gating, or the like is employed. In the case of a displaydevice, the number of times of display refreshing is reduced in asuggested method. However, when the refreshing interval of display islong, leakage of electric charges occurs in a switch transistorretaining data. The retained data is deteriorated by the leakage ofelectric charges, which causes flickers to reduce the viewability.

In view of the above problems, an object of one embodiment of thepresent invention is to provide a display device with improvedoperability in touch input. Another object of one embodiment of thepresent invention is to provide a display device with a novel structureincluding a touch sensor. Another object of one embodiment of thepresent invention is to provide an electronic device with reduced powerconsumption.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

Note that the objects of one embodiment of the present invention are notlimited to the above objects. The objects described above do not disturbthe existence of other objects. The other objects are the ones that arenot described above and will be described below. The other objects willbe apparent from and can be derived from the description of thespecification, the drawings, and the like by those skilled in the art.One embodiment of the present invention is to solve at least one of theaforementioned objects and the other objects.

One embodiment of the present invention is a display device thatincludes a gate driver, a plurality of touch sensors, and a plurality ofwirings. The plurality of wirings are respectively connected to theplurality of touch sensors. The gate driver has a function of supplyinga scan signal to the plurality of wirings at the same timing. Theplurality of touch sensors in different positions have a function ofsensing a plurality of touches at the same timing.

One embodiment of the present invention is a display device thatincludes a display region and a gate driver. The display region includesa plurality of pixels, a plurality of touch sensors, a plurality of scanlines, and a plurality of touch wirings. The gate driver has a functionof supplying a first scan signal to the plurality of scan lines. Thegate driver has a function of supplying a second scan signal for sensinga touch to the plurality of touch wirings.

In the above display devices, it is preferable that the pixel include afirst display element and the first display element be a transmissiveliquid crystal element.

In the above display devices, it is preferable that the pixel include afirst display element and the first display element be a reflectiveliquid crystal element.

In the above display device, the pixel preferably includes the firstdisplay element and a second display element. The first display elementpreferably has a function of reflecting visible light. The seconddisplay element preferably has a function of emitting visible light.

In the above display device, the second display element is preferably alight-emitting element.

The above display devices preferably include a transistor and thetransistor preferably includes polysilicon in a semiconductor layer.

The above display devices preferably include a transistor and thetransistor preferably includes a metal oxide in a semiconductor layer.

In the above display devices, an image is preferably displayed with oneor both of first light reflected by the first display element and secondlight emitted by the second display element.

According to one embodiment of the present invention, a display devicewith improved operability in touch input can be provided. According toanother embodiment of the present invention, a display device with anovel structure including a touch sensor can be provided. According toanother embodiment of the present invention, an electronic device withreduced power consumption can be provided.

Note that the effects of one embodiment of the present invention are notlimited to the above effects. The effects described above do not disturbthe existence of other effects. The other effects are the ones that arenot described above and will be described below. The other effects willbe apparent from and can be derived from the description of thespecification, the drawings, and the like by those skilled in the art.One embodiment of the present invention is to have at least one of theaforementioned effects and the other effects. Accordingly, oneembodiment of the present invention does not have the aforementionedeffects in some cases.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates driving timing of a touch sensor and FIG. 1B is ablock diagram illustrating a display device.

FIG. 2 is a block diagram illustrating a gate driver.

FIG. 3 is a circuit diagram illustrating touch sensors and pixels in adisplay device.

FIG. 4 is a circuit diagram illustrating touch sensors and pixels in adisplay device.

FIGS. 5A to 5C are schematic cross-sectional views each illustrating amode employed in a display device.

FIGS. 6A and 6B are schematic cross-sectional views each illustrating amode employed in a display device.

FIGS. 7A and 7B are top views each illustrating a structure of a touchsensor in a display device.

FIGS. 8A and 8B are a top view and a schematic cross-sectional view of adisplay device.

FIG. 9 is a schematic cross-sectional view of a display device.

FIGS. 10A to 10D are schematic views illustrating a structure of a pixelin a display device.

FIGS. 11A and 11B are cross-sectional views illustrating a structure ofa pixel in a display device.

FIGS. 12A and 12B are cross-sectional views illustrating a structure ofa pixel in a display device.

FIGS. 13A and 13B are cross-sectional views illustrating a structure ofa pixel in a display device.

FIGS. 14A and 14B are cross-sectional views illustrating a structure ofa pixel in a display device.

FIGS. 15A to 15C are top views and a cross-sectional view illustrating astructure of a display device.

FIGS. 16A to 16C are cross-sectional views illustrating a structure of adisplay device.

FIG. 17 is a cross-sectional view illustrating a structure of a displaydevice.

FIGS. 18A and 18B are bottom views each illustrating a structure of apixel in a display device.

FIG. 19 is a circuit diagram illustrating a pixel circuit in a displaydevice.

FIGS. 20A to 20D are cross-sectional views each illustrating a structureof a reflective film in a display device.

FIGS. 21A to 21C are top views each illustrating a structure of areflective film in a display device.

FIGS. 22A and 22B are top views illustrating pixels and subpixels in adisplay device.

FIGS. 23A-1, 23A-2, 23B-1, 23B-2, 23C-1, 23C-2, 23D-1, 23D-2, 23E-1,23E-2, 23F-1, and 23F-2 are cross-sectional views and perspective viewsillustrating shapes of an optical element in a display device.

FIGS. 24A to 24C each illustrate operation of a display device.

FIGS. 25A to 25E each illustrate a structural example of an electronicdevice.

FIGS. 26A to 26E each illustrate a structural example of an electronicdevice.

FIG. 27 shows measured XRD spectra of samples.

FIGS. 28A and 28B are TEM images of samples and FIGS. 28C to 28L areelectron diffraction patterns thereof.

FIGS. 29A to 29C show EDX mapping images of a sample.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments will be described with reference to drawings.Note that the embodiments can be implemented in many different modes,and it will be readily appreciated by those skilled in the art thatmodes and details thereof can be changed in various ways withoutdeparting from the spirit and scope of the present invention. Thus, thepresent invention should not be interpreted as being limited to thefollowing description of the embodiments.

In the drawings, the size, the layer thickness, or the region isexaggerated for clarity in some cases. Therefore, embodiments of thepresent invention are not limited to such a scale. Note that thedrawings are schematic views showing ideal examples, and embodiments ofthe present invention are not limited to shapes or values shown in thedrawings.

Note that in this specification, ordinal numbers such as “first”,“second”, and “third” are used in order to avoid confusion amongcomponents, and the terms do not limit the components numerically.

Note that in this specification, terms for describing arrangement, suchas “over” “above”, “under”, and “below”, are used for convenience indescribing a positional relation between components with reference todrawings. Further, the positional relation between components is changedas appropriate in accordance with a direction in which the componentsare described. Thus, the positional relation is not limited to thatdescribed with a term used in this specification and can be explainedwith another term as appropriate depending on the situation.

In this specification and the like, a transistor is an element having atleast three terminals of a gate, a drain, and a source. In addition, thetransistor has a channel region between a drain (a drain terminal, adrain region, or a drain electrode) and a source (a source terminal, asource region, or a source electrode), and current can flow through thechannel region between the source region and the drain region. Note thatin this specification and the like, a channel region refers to a regionthrough which current mainly flows.

Further, functions of a source and a drain might be switched whentransistors having different polarities are employed or a direction ofcurrent flow is changed in circuit operation, for example. Therefore,the terms “source” and “drain” can be switched in this specification andthe like.

Note that in this specification and the like, the expression“electrically connected” includes the case where components areconnected through an “object having any electric function”. There is noparticular limitation on an “object having any electric function” aslong as electrical signals can be transmitted and received betweencomponents that are connected through the object. Examples of an “objecthaving any electric function” are a switching element such as atransistor, a resistor, an inductor, a capacitor, and elements with avariety of functions as well as an electrode and a wiring.

In this specification and the like, the term “parallel” means that theangle formed between two straight lines is greater than or equal to −10°and less than or equal to 10°, and accordingly also covers the casewhere the angle is greater than or equal to −5° and less than or equalto 5°. The term “perpendicular” means that the angle formed between twostraight lines is greater than or equal to 80° and less than or equal to100°, and accordingly also covers the case where the angle is greaterthan or equal to 85° and less than or equal to 95°.

In this specification and the like, the terms “film” and “layer” can beinterchanged with each other. For example, the term “conductive layer”can be changed into the term “conductive film” in some cases. Also, theterm “insulating film” can be changed into the term “insulating layer”in some cases.

Unless otherwise specified, the off-state current in this specificationand the like refers to a drain current of a transistor in the off state(also referred to as non-conduction state and cutoff state). Unlessotherwise specified, the off state of an n-channel transistor means thata voltage (V_(gs)) between its gate and source is lower than thethreshold voltage (V_(th)), and the off state of a p-channel transistormeans that the gate-source voltage V_(gs) is higher than the thresholdvoltage V_(th). For example, the off-state current of an n-channeltransistor sometimes refers to a drain current that flows when thegate-source voltage V_(gs) is lower than the threshold voltage V_(th).

The off-state current of a transistor depends on V_(gs) in some cases.Thus, “the off-state current of a transistor is lower than or equal toI” may mean “there is V_(gs) with which the off-state current of thetransistor becomes lower than or equal to I”. Furthermore, “theoff-state current of a transistor” means “the off-state current in anoff state at predetermined V_(gs)”, “the off-state current in an offstate at V_(gs) in a predetermined range”, “the off-state current in anoff state at V_(gs) with which sufficiently reduced off-state current isobtained”, or the like.

As an example, the assumption is made of an n-channel transistor wherethe threshold voltage V_(th) is 0.5 V and the drain current is 1×10⁻⁹ Aat V_(gs) of 0.5 V, 1×10⁻¹³ A at V_(gs) of 0.1 V, 1×10⁻¹⁹ A at V_(gs) of−0.5 V, and 1×10⁻²² A at V_(gs) of −0.8 V. The drain current of thetransistor is 1×10⁻¹⁹ A or lower at V_(gs) of −0.5 V or at V_(gs) in therange of −0.8 V to −0.5 V; therefore, it can be said that the off-statecurrent of the transistor is 1×10⁻¹⁹ A or lower. Since there is V_(gs)at which the drain current of the transistor is 1×10⁻²² A or lower, itmay be said that the off-state current of the transistor is 1×10⁻²² A orlower.

In this specification and the like, the off-state current of atransistor with a channel width W is sometimes represented by a currentvalue in relation to the channel width W or by a current value per givenchannel width (e.g., 1 μm). In the latter case, the off-state currentmay be expressed in the unit with the dimension of current per length(e.g., A/μm).

The off-state current of a transistor depends on temperature in somecases. Unless otherwise specified, the off-state current in thisspecification may be an off-state current at room temperature, 60° C.,85° C., 95° C., or 125° C. Alternatively, the off-state current may bean off-state current at a temperature at which the reliability requiredin a semiconductor device or the like including the transistor isensured or a temperature at which the semiconductor device or the likeincluding the transistor is used (e.g., temperature in the range of 5°C. to 35° C.). The description “an off-state current of a transistor islower than or equal to I” may refer to a situation where there is V_(gs)at which the off-state current of a transistor is lower than or equal toI at room temperature, 60° C., 85° C., 95° C., 125° C., a temperature atwhich the reliability required in a semiconductor device or the likeincluding the transistor is ensured, or a temperature at which thesemiconductor device or the like including the transistor is used (e.g.,temperature in the range of 5° C. to 35° C.).

The off-state current of a transistor depends on voltage V_(ds) betweenits drain and source in some cases. Unless otherwise specified, theoff-state current in this specification may be an off-state current atV_(ds) of 0.1 V, 0.8 V, 1 V, 1.2 V, 1.8 V, 2.5 V, 3 V, 3.3 V, 10 V, 12V, 16 V, or 20 V. Alternatively, the off-state current might be anoff-state current at V_(ds) at which the required reliability of asemiconductor device or the like including the transistor is ensured orV_(ds) at which the semiconductor device or the like including thetransistor is used. The description “an off-state current of atransistor is lower than or equal to I” may refer to a situation wherethere is V_(gs) at which the off-state current of a transistor is lowerthan or equal to I at V_(ds) of 0.1 V, 0.8 V, 1 V, 1.2 V, 1.8 V, 2.5 V,3 V, 3.3 V, 10 V, 12 V, 16 V, or 20 V, V_(ds) at which the requiredreliability of a semiconductor device or the like including thetransistor is ensured, or V_(ds) at which the semiconductor device orthe like including the transistor is used.

In the above description of off-state current, a drain may be replacedwith a source. That is, the off-state current sometimes refers to acurrent that flows through a source of a transistor in the off state.

In this specification and the like, the term “leakage current” sometimesexpresses the same meaning as off-state current. In this specificationand the like, the off-state current sometimes refers to a current thatflows between a source and a drain when a transistor is off, forexample.

Note that a voltage refers to a difference between potentials of twopoints, and a potential refers to electrostatic energy (electricpotential energy) of a unit charge at a given point in an electrostaticfield. Note that in general, a difference between a potential of onepoint and a reference potential (e.g., a ground potential) is merelycalled a potential or a voltage, and “potential” and “voltage” are usedas synonymous words in many cases. Therefore, in this specification,“potential” can be replaced with “voltage” and vice versa, unlessotherwise specified.

Embodiment 1

In this embodiment, an in-cell touch sensor whose operability in touchsensing is improved is described with reference to FIGS. 1A and 1B, FIG.2, FIG. 3, FIG. 4, FIGS. 5A to 5C, FIGS. 6A and 6B, FIGS. 7A and 7B,FIGS. 8A and 8B, and FIG. 9.

FIG. 1A illustrates driving timing of a display device 10 including atouch sensor. FIG. 1B is a block diagram of the display device 10. As anexample, FIG. 1A illustrates displaying 60 frames in one second. Oneframe is a period in which all the data of pixels included in thedisplay device are refreshed. One frame period is approximately 16.6 ms.

In FIG. 1A, one frame period includes a period T0-T1 in which display isrefreshed and a period T1-T3 in which a touch by a sensing target issensed with a touch sensor. The period T0-T1 in which display isrefreshed and the period T1-T3 in which touch sensing is performed mayhave the same length or alternatively, the period T1-T3 in which touchsensing is performed may be longer than the period T0-T1 in whichdisplay is refreshed. Further alternatively, the period T0-T1 in whichdisplay is refreshed may be longer than the period T1-T3 in which touchsensing is performed. FIG. 1A illustrates an example in which the periodT0-T1 in which display is refreshed and the period T1-T3 in which touchsensing is performed are controlled to have the same length.

FIG. 1A illustrates an example in which in one frame period T0-T3,display is refreshed in the period T0-T1 and touch sensing is performedin the rest period T1-T3. The period in which touch sensing is performedfurther includes two periods T1-T2 and T2-T3 in each of which touchsensing is performed. When the number of times of touch sensing is setto two or more, touch sensing accuracy can be increased. Note that touchsensing may be performed in only one period.

The touch sensing accuracy increases when one frame period includes alarger number of periods in which touch sensing is performed. In theexample illustrated in FIG. 1A, a non-sensing period with a duration ofapproximately 8 ms and two sensing periods each with a duration of 4 msare provided. When the number of periods in which touch sensing isperformed is two or more, touch sensing accuracy can be increased.

The control signal supplied in refreshing display causes noise andsensing errors by the touch sensor occur; thus, in the period in whichdisplay is refreshed, touch sensing is preferably suspended. Inaddition, display is not refreshed in the period in which touch sensingis performed. It is thus preferable that a circuit for refreshingdisplay not operate in the period in which touch sensing is performed.In addition, a selection transistor for retaining the data to bedisplayed preferably has a low leakage current in an off state. Thepixels will be described in detail with reference to FIG. 3. Thetransistor with a low leakage current will be described in detail inEmbodiment 4.

A touch sensor based on any of a variety of operation principles may beused, such as a projected capacitive touch sensor, a surface capacitivetouch sensor, a resistive touch sensor, or an optical touch sensor. Inany type of sensors, data is input when a sensing target touches orapproaches the touch sensor. In an example in this embodiment, aprojected capacitive touch sensor is used.

The display device 10 in FIG. 1B includes a gate driver 61 that drivesthe touch sensor and controls signal lines in the row direction, thereceiver circuit 62 that senses a touch, and a plurality of touchsensors 63. The gate driver 61 is electrically connected to the touchsensors 63 and pixels 64. In the example illustrated in FIG. 1B, thepixels 64 are provided to overlap with the touch sensor 63(1,6).

The touch sensor 63 includes pixels, a touch wiring COM-Tx supplied witha scan signal for the touch sensor, and a touch wiring COM-Rxtransmitting sensing of a touch as an electrical signal. To the pixels,which will be described in detail with reference to FIG. 3, a scan linefor refreshing display, a signal line, and a wiring CSCOM areelectrically connected. The details of the touch sensor 63 will bedescribed with reference to FIG. 3. Although the touch sensors 63 arearranged in a 6×6 matrix in the example illustrated in FIG. 1B, thenumber of the touch sensors 63 can be set as appropriate.

Details of the driving timing illustrated in FIG. 1A will be describedwith reference to the block diagram in FIG. 1B. With the driving timingin the example illustrated in FIG. 1A, the touch sensor 63(1,1) and thetouch sensor 63(1,4) concurrently perform touch sensing.

When the touch sensor 63(1,1) and the touch sensor 63(1,4) that aredistanced perform sensing, the distance between the two touch sensors 63prevents the interference of scan signals supplied at the same timing.Therefore, the two touch sensors 63 can perform touch sensing at thesame timing.

The touch sensors provided in a display region can be scanned inone-half the time. In other words, the touch sensors can be scanned at afrequency twice the frequency in row-by-row scanning. Scan signals aresupplied to the touch wirings COM-Tx in two rows at the same time in theexample illustrated in FIGS. 1A and 1B; however, when a touch sensingregion is wide, scan signals may be supplied to the touch wirings inthree or more rows at the same time.

FIG. 2 illustrates the gate driver 61. The gate driver 61 has a functionof supplying a scan signal for refreshing display to the scan line and afunction of supplying a scan signal to be supplied to the touch sensorto the touch wiring. In the drawing, n represents an integer of one ormore.

The gate driver 61 includes a decoder 61 a, a plurality of selectioncircuits 61 b, and a plurality of buffers 61 g. The selection circuit 61b includes a shift register 61 c, a switch 61 d, a switch 61 e, and aswitch 61 f.

A terminal 2 of the switch 61 d is electrically connected to a scan line65(1) through the buffer 61 g. A terminal 2 of the switch 61 e iselectrically connected to a scan line 65(2) through the buffer 61 g. Aterminal 2 of the switch 61 f is electrically connected to the touchwiring COM-Tx through the buffer 61 g.

To the decoder 61 a, a wiring ADD and a wiring CTRL are electricallyconnected. Output signals DE are generated from a signal Address that issupplied to the wiring ADD. It is preferable that a plurality of signalsAddress be supplied to a plurality of wirings ADD. Furthermore, a signalSel that is supplied to the wiring CTRL allows switching between a scansignal for refreshing display and a scan signal for sensing a touch thatare to be output. For example, “L” is supplied as the signal Sel torefresh display and “H” is supplied as the signal Sel to control thetouch sensor, whereby the output signal DE can be used as differentkinds of scan signals.

The selection circuit 61 b can supply a plurality of scan signals GOUTto the scan lines through the buffer 61 g. The number of scan lineselectrically connected to the selection circuit 61 b can be setappropriately in accordance with the number of pixels connected to onetouch sensor 63.

The shift register 61 c has a function of sequentially outputtingsignals SR(1) to SR(6) when “L” is supplied as the signal Sel.

When “L” is supplied as the signal Sel, a terminal 1 and the terminal 2of the switch 61 d are electrically connected to each other and thesignal SR(1) is output to a wiring ND1. The signal supplied to thewiring ND1 is supplied to the scan line 65(1) as the scan signal GOUT(1)through the buffer 61 g.

When “L” is supplied as the signal Sel, a terminal 1 and the terminal 2of the switch 61 e are electrically connected to each other and thesignal SR(2) is output to a wiring ND2. The signal supplied to thewiring ND2 is supplied to the scan line 65(2) as the scan signal GOUT(2)through the buffer 61 g.

When “L” is supplied as the signal Sel, a terminal 3 and the terminal 2of the switch 61 f are electrically connected to each other and a commonpotential supplied to a wiring COM can be supplied to the touch wiringCOM-Tx through the buffer 61 g.

When “H” is supplied as the signal Sel, a terminal 3 and the terminal 2of the switch 61 d are electrically connected to each other and an L1potential, which is supplied to a wiring GVSS, is output to the wiringND1. The L1 potential supplied to the wiring ND1 is supplied to the scanline 65(1) as the scan signal GOUT(1) through the buffer 61 g. The L1potential is the lowest potential to be supplied to the scan line.

When “H” is supplied as the signal Sel, a terminal 3 and the terminal 2of the switch 61 e are electrically connected to each other and the L1potential, which is supplied to the wiring GVSS, is output to the wiringND2. The L1 potential supplied to the wiring ND2 is supplied to the scanline 65(2) as the scan signal GOUT(2) through the buffer 61 g.

When “H” is supplied as the signal Sel, a terminal 1 and the terminal 2of the switch 61 f are electrically connected to each other and thesignal DE(1) is output to a wiring ND3. The signal supplied to thewiring ND3 can be supplied to the touch wiring COM-Tx as a scan signalthrough the buffer 61 g.

The period in which the signal Sel is “H” is the period in which touchsensing is performed; the L1 potential is supplied to the scan lines andoutput of the decoder is supplied to the touch wiring COM-Tx as a scansignal.

The touch sensor 63 illustrated in FIG. 3 includes a plurality of pixels64. In the example illustrated in FIG. 3, one touch sensor 63 includessix pixels 64. When the gate driver 61 in FIG. 2 is used for control,the shift register 61 c preferably has two stages.

The pixel 64 includes a selection transistor 64 a, a capacitor 64 b, anda liquid crystal display element 64 c. The liquid crystal displayelement 64 c includes a pixel electrode 68 (which is illustrated inFIGS. 7A and 7B) and a liquid crystal whose alignment changes with thepotential difference between the pixel electrode 68 and the wiringCSCOM.

Here, the touch sensor 63(1,1) is described as an example. A gate of theselection transistor 64 a is electrically connected to the scan line65(1). One of a source and a drain of the selection transistor 64 a iselectrically connected to a signal line 66. The pixel electrode 68 andone electrode of the capacitor 64 b are electrically connected to theother of the source and the drain of the selection transistor 64 a. Theother electrode of the capacitor 64 b is electrically connected to thewiring CSCOM.

The touch wiring COM-Rx(1) is provided in the touch sensor 63(1,1). Thetouch wiring COM-Rx(1) serves as one electrode of a sensor element ofthe touch sensor, and the touch wiring COM-Tx(1) serves as the otherelectrode of the sensor element of the touch sensor. Thus, in the touchsensor 63(1,1), a capacitor 67 the pair of electrodes of which are thetouch wiring COM-Tx(1) and the touch wiring COM-Rx(1) is formed as thesensor element.

When the touch wiring COM-Tx and the touch wiring COM-Rx operate as partof the touch sensor 63, a scan signal is supplied to the touch wiringCOM-Tx as illustrated in FIG. 2. Thus, whether or not touch operation isperformed can be sensed in accordance with the amount of change in theelectrical signal transmitted by the touch wiring COM-Rx. Accordingly,the touch sensors 63 can independently sense whether or not touchoperation is performed.

With the configuration illustrated in FIG. 3, the touch sensor 63(1,1)and the touch sensor 63(1,4) can concurrently perform touch sensing asillustrated in FIG. 1B. Since one electrode of each sensor element isindependent, the touch sensors do not affect each other. The touchsensor 63(1,1), the touch sensor 63(2,1), the touch sensor 63(3,4), andthe touch sensor 63(4,4) can perform sensing concurrently, for example.

In this manner, the touch sensors 63 in a specific region canselectively perform sensing and thus the touch sensor function can bepartly activated or deactivated in accordance with display when, forexample, only part of display is refreshed.

A configuration different from that of the touch sensor 63 in FIG. 3 isdescribed with reference to FIG. 4.

A difference is that the wiring CSCOM is electrically connected to aterminal 2 of a switch 61 h. A terminal 1 of the switch 61 h iselectrically connected to the wiring COM. A terminal 3 of the switch 61h is electrically connected to the touch wiring COM-Rx.

The switch 61 h is electrically connected to the wiring CTRL and issupplied with the signal Sel. In the period when the signal Sel is “L”,the terminal 1 and the terminal 2 of the switch 61 h are electricallyconnected to each other, so that the common potential supplied to thewiring COM is supplied to the wiring CSCOM. In the period when thesignal Sel is “H”, the terminal 2 and the terminal 3 of the switch 61 hare electrically connected to each other, so that a sensing signal Senof the wiring CSCOM is output to the touch wiring COM-Rx.

Thus, a common potential is supplied to the wiring CSCOM as a referencepotential of the liquid crystal display element 64 c when pixels performdisplay. When the wiring CSCOM operates as part of the touch sensor, thewiring CSCOM serves as one electrode of the sensor element of the touchsensor, and the touch wiring COM-Tx serves as the other electrode of thesensor element of the touch sensor.

As the sensor element of the touch sensor 63, the capacitor 67 the pairof electrodes of which are the touch wiring COM-Tx and the wiring CSCOMis formed. In the period in which the signal Sel is “L”, a commonpotential is supplied to the touch wiring COM-Tx and the wiring CSCOMthrough the wiring COM, so that the capacitance of the capacitor 67 iscancelled; thus, display quality is not adversely affected.

In the period in which the signal Sel is “H”, the wiring CSCOM functionsas one electrode of the sensor element of the touch sensor; thus, theoff-state current of the selection transistor 64 a in the pixel 64 needsto be low.

When the touch wiring COM-Tx and the wiring CSCOM operate as part of thetouch sensor, a scan signal is supplied to the touch wiring COM-Tx asillustrated in FIG. 2. The liquid crystal display element 64 c expressesgray levels of display with the use of a liquid crystal whose alignmentdirection changes with the potential difference between the pixelelectrode and the wiring CSCOM. It is thus preferable that thegray-level voltage held in the capacitor 64 b not change. When theoff-state current of the selection transistor 64 a is low, leakagethrough the selection transistor 64 a can be minimized. Even if thevoltage value of the wiring CSCOM changes, a change in gray level can beminimized owing to the low off-state current of the selectiontransistor.

The gate driver 61 illustrated in FIG. 2 can control both display andtouch sensing. The display and touch sensing can be controlled atdifferent timings. Thus, the signal/noise ratio (SN ratio) of the touchsensor can be high, increasing the sensing accuracy.

FIGS. 5A to 5C are schematic cross-sectional views each illustrating thetouch sensor of the display device 10. Note that in the schematiccross-sectional views in FIGS. 5A to 5C, only the components necessaryfor describing the operation of the touch sensor are illustrated. Forexample, an element such as a transistor is sometimes provided over asubstrate 11 but is not illustrated in the drawings.

The touch sensor illustrated in FIG. 5A includes the substrate 11, asubstrate 12, an FPC 13, a conductive layer 14, a liquid crystal element20, a coloring film 31, and the like.

The liquid crystal element 20 includes a conductive layer 21, aconductive layer 22, and a liquid crystal 23. The conductive layer 22 ispositioned over the conductive layer 21 with an insulating layer 24provided therebetween. The conductive layer 21 functions as a pixelelectrode of the liquid crystal element 20 and the conductive layer 22functions as a common electrode.

The conductive layer 21 and the conductive layer 22 are provided so asto form an electric field intersecting the thickness direction of theliquid crystal 23 (the A1-A2 direction in the drawing).

The touch sensor can perform sensing by utilizing the capacitance formedbetween the conductive layer 22 a or 22 b on the substrate 11 side thatserves as one of a pair of electrodes of the liquid crystal element 20and the conductive layer 22 c serving as the touch wiring COM-Tx.

In the example illustrated in FIG. 5B, the conductive layers 21 a and 21b serving as the pixel electrodes of the liquid crystal elements 20 alsoserve as the pair of electrodes of the touch sensor.

In the example illustrated in FIG. 5C, the conductive layers 22 a and 22b serving as the common electrodes of the liquid crystal elements 20also serve as the pair of electrodes of the touch sensor.

In the structure illustrated in FIG. 5A, one electrode of the liquidcrystal element 20 can also serve as one electrode of the touch sensor.With the structure illustrated in FIG. 5B or 5C, one electrode of theliquid crystal element 20 can serve as the pair of electrodes of thetouch sensor.

The conductive layer 22 a, the conductive layer 22 b, and the conductivelayer 22 c can be formed using one conductive layer, which simplifiesthe process. The conductive layer 21 a and the conductive layer 21 b canalso be formed using one conductive layer, which simplifies the process.

The schematic cross-sectional view in FIG. 6A illustrates a lightextraction method using FIG. 5A.

FIG. 6A illustrates an example in which the conductive layer 21 and theconductive layer 22 are formed using light-transmitting conductivelayers. In that case, the display device 10 preferably includes a lightsource emitting visible light L1, under the substrate 11. The visiblelight L1 incident through the substrate 11 can be emitted toward thesubstrate 12 after the gray level of the light is controlled with theliquid crystal element sandwiched between the substrate 11 and thesubstrate 12.

The structure illustrated in FIG. 6B is different from that illustratedin FIG. 6A in that the conductive layer 21 is formed using a conductivelayer that reflects visible light. Accordingly, light L2 incidentthrough the substrate 12 is reflected by the conductive layer 21 to beemitted to the outside through the substrate 12.

When utilizing external light, display can be performed without a lightsource unlike in the display device illustrated in FIG. 6A. As a result,the number of components of the display device can be reduced.Furthermore, there is no power consumed by a light source. In a brightenvironment such as an environment under sunlight, the luminance of thereflected light increases in proportion to the luminance of the externallight, which increases the viewability.

The conductive layer reflecting visible light preferably has highreflectance. High reflectance leads to high luminance at the time ofreflective display using external light.

For example, a material containing one of indium (In), zinc (Zn), andtin (Sn) is preferably used for the conductive material that transmitsvisible light. Specifically, indium oxide, indium tin oxide, indium zincoxide, indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, indium tin oxide containingsilicon oxide, zinc oxide, and zinc oxide containing gallium are given,for example. Note that a film including graphene can be used as well.The film including graphene can be formed, for example, by reducing afilm containing graphene oxide.

Examples of a conductive material that reflects visible light includealuminum, silver, and an alloy including any of these metal elements.Furthermore, a metal material such as gold, platinum, nickel, tungsten,chromium, molybdenum, iron, cobalt, copper, or palladium or an alloycontaining any of these metal materials can be used. Furthermore,lanthanum, neodymium, germanium, or the like may be added to the metalmaterial or the alloy. Furthermore, an alloy containing aluminum (analuminum alloy) such as an alloy of aluminum and titanium, an alloy ofaluminum and nickel, an alloy of aluminum and neodymium, or an alloy ofaluminum, nickel, and lanthanum (Al—Ni—La), or an alloy containingsilver such as an alloy of silver and copper, an alloy of silver,palladium, and copper (also referred to as Ag—Pd—Cu or APC), or an alloyof silver and magnesium may be used.

FIG. 7A is a top view of the touch sensor 63 illustrated in FIG. 3. Thetouch sensor 63 including six pixels 64 is described using the exampleillustrated in FIG. 3. The touch sensor 63 may include a plurality ofpixels 64 and the number of the pixels 64 is not limited. The top viewin FIG. 7A illustrates an example in which an R element, a G element,and a B element (the coloring film 31 in FIGS. 5A to 5C) are provided ina stripe shape.

The structure illustrated in FIG. 7A includes a plurality of scan lines65, a plurality of signal lines 66, the wiring CSCOM, the touch wiringCOM-Tx, the touch wiring COM-Rx, and a plurality of pixels 64. Each ofthe pixels 64 includes the selection transistor 64 a, the capacitor 64b, and the pixel electrode 68.

As an example, the pixel 64 connected to a scan line 65 a is described.The gate of the selection transistor 64 a in the pixel 64 iselectrically connected to the scan line 65 a. One of the source and thedrain of the selection transistor 64 a is electrically connected to thesignal line 66R. Furthermore, one electrode of the capacitor 64 b isformed using the same conductive layer as the other of the source andthe drain of the selection transistor 64 a. The capacitor 64 b is formedin a region overlapping with the wiring CSCOM. The pixel electrode 68 isformed using the same conductive layer as the other of the source andthe drain of the selection transistor 64 a.

The other electrode of the capacitor 64 b is electrically connected to acommon electrode 64 f through a contact 64 d. The gray level of displayis controlled by the liquid crystal whose alignment direction changeswith the potential difference between the pixel electrode 68 and thecommon electrode 64 f. Therefore, the liquid crystal 23 is provided overthe common electrode 64 f as illustrated in FIG. 5A.

The touch wiring COM-Rx is electrically connected to a wiring 64 hthrough a contact 64 g. In the touch sensor 63, the capacitor 67 with asensing function is formed with the wiring 64 h and the touch wiringCOM-Tx serving as a pair of electrodes. Thus, the touch wiring COM-Txand the touch wiring COM-Rx are preferably formed using the sameconductive layer.

Although the touch wiring COM-Rx(2) and the touch wiring COM-Rx(3) areillustrated in FIG. 7A, they are electrically connected to a touchsensor provided in a position different from that of the touch sensor 63illustrated in FIG. 7A. The touch wiring COM-Rx may be provided asappropriate and as needed depending on the number of the pixels 64 inthe touch sensor 63. Accordingly, when the touch sensor 63 includes manypixels 64, the touch wiring COM-Rx(2) and the touch wiring COM-Rx(3)illustrated in FIG. 7A are not necessarily provided.

The sensitivity of the touch sensor 63 can be controlled by changing thesize of the capacitor 67 having the sensing function. Since the numberof pixels in the touch sensor 63 and the size of the capacitor 67 areproportional to each other, the number of the pixels 64 and the numberof the touch wirings COM-Tx can be selected as appropriate such that thesize of the capacitor 67 is optimized.

FIG. 7B is a top view of the touch sensor 63 illustrated in FIG. 4. Astructure different from that in FIG. 7A is described.

The structure illustrated in FIG. 7B includes the plurality of scanlines 65, the plurality of signal lines 66, a plurality of wiringsCSCOM, the touch wiring COM-Tx, and the plurality of pixels 64. Each ofthe pixels 64 includes the selection transistor 64 a, the capacitor 64b, and the pixel electrode 68.

A difference is that one electrode of the capacitor 64 b is electricallyconnected to the wiring CSCOM(1) through a contact 64 e. The wiringCSCOM(1) serves as a common electrode in each of the pixels 64 in thetouch sensor 63.

Although the wiring CSCOM(2) and the wiring CSCOM(3) are illustrated inFIG. 7B, they are electrically connected to a touch sensor provided in aposition different from that of the touch sensor 63 illustrated in FIG.7B. The wiring CSCOM may be provided as needed depending on the numberof the pixels 64 in the touch sensor 63. Accordingly, when the touchsensor 63 includes many pixels 64, the wiring CSCOM(2) and the wiringCSCOM(3) illustrated in FIG. 7B are not necessarily provided.

The touch wiring COM-Tx is equidistant from the common electrodes 64 fof the pixels. The capacitor 67 having a sensing function is formed withthe touch wiring COM-Tx and the common electrode 64 f serving as a pairof electrodes. Thus, the touch wiring COM-Tx and the common electrode 64f are preferably formed using the same conductive layer.

<Cross-Sectional Structure of Display Device>

A cross-sectional structure of a display device functioning as anin-cell touch panel is described as an example. As typical examples ofthe in-cell touch panel, a hybrid in-cell type and a full-in-cell typecan be given. A cross-sectional structure of a full-in-cell touch panelusing a liquid crystal element as a display element is described below.The full-in-cell touch panel using a liquid crystal element as a displayelement functions as a liquid crystal display device.

In the case of a liquid crystal display device functioning as afull-in-cell touch panel, a structure of a counter substrate can besimplified, which is preferable. The liquid crystal display device ispreferable because an electrode constituting a part of the displayelement also serves as an electrode constituting a part of the sensorelement and thus the manufacturing process can be simplified and themanufacturing cost can be reduced.

FIG. 8A is a top view of a liquid crystal display device 200 that canfunction as a touch panel. FIG. 8B is a cross-sectional view taken alongdashed-dotted lines A-B and C-D in FIG. 8A.

As illustrated in FIG. 8A, the liquid crystal display device 200includes a display portion 201 and gate line driver circuits 202. Thedisplay portion 201 includes a plurality of pixels 203, a plurality ofsource lines, and a plurality of gate lines, and has a function ofdisplaying an image. Moreover, the display portion 201 also serves as aninput portion. That is, the display portion includes a plurality ofsensor elements that can sense touch or proximity of a sensing target tothe liquid crystal display device 200 and thus serves as a touch sensor.The gate line driver circuit 202 has a function of outputting a scansignal to the gate lines included in the display portion 201. The pixel203 includes a plurality of subpixels. Although FIG. 8A illustrates anexample in which the pixel 203 includes three subpixels, one embodimentof the present invention is not limited to this example.

Although FIG. 8A illustrates an example in which the liquid crystaldisplay device 200 includes the gate line driver circuits, oneembodiment of the present invention is not limited to this example. Theliquid crystal display device 200 that does not include any of a gateline driver circuit, a source line driver circuit, and a sensor drivercircuit may be employed, or the liquid crystal display device 200 thatincludes any one or more of a gate line driver circuit, a source linedriver circuit, and a sensor driver circuit may be employed.

In the liquid crystal display device 200, an IC 368 is mounted on asubstrate 311 by a COG method or the like. The IC 368 includes, forexample, any one or more of a source line driver circuit, a gate linedriver circuit, and a sensor driver circuit.

An FPC 369 is connected to the liquid crystal display device 200. The IC368 and the gate line driver circuits are supplied with a signal fromthe outside via the FPC 369. Furthermore, a signal can be output fromthe IC 368 to the outside via the FPC 369.

An IC may be mounted on the FPC 369. For example, an IC including anyone or more of a source line driver circuit, a gate line driver circuit,and a sensor driver circuit may be mounted on the FPC 369. For example,the IC may be mounted on the FPC 369 by a COF method or a tape automatedbonding (TAB) method.

For example, the IC 368 may include a source line driver circuit and asensor driver circuit. Alternatively, for example, the IC 368 mayinclude a source line driver circuit and the IC mounted on the FPC 369may include a sensor driver circuit.

As illustrated in FIG. 8B, the liquid crystal display device 200includes a transistor 380 a, a transistor 370 a, a connection portion305 a, a liquid crystal element 307 a, and the like over the substrate311.

FIG. 8B illustrates the cross section of one subpixel as an example ofthe display portion 201. For example, a subpixel exhibiting a red color,a subpixel exhibiting a green color, and a subpixel exhibiting a bluecolor form one pixel, and thus full-color display can be achieved in thedisplay portion 201. Note that the color exhibited by subpixels is notlimited to red, green, and blue. For example, a subpixel exhibitingwhite, yellow, magenta, cyan, or the like may be used for a pixel.

The transistors 380 a and 370 a each include a conductive layer 373, aninsulating layer 312, an insulating layer 315, an insulating layer 313,a polysilicon film 372, a conductive layer 374 a, and a conductive layer374 b.

The conductive layer 373 can function as a gate or a back gate. Theconductive layer 374 a can function as one of a source electrode and adrain electrode. The conductive layer 374 b can function as the other ofthe source electrode and the drain electrode.

The polysilicon film 372 includes an impurity region that is formed byadding an impurity element. The polysilicon film 372 may include alightly doped drain (LDD) region that is formed by adding an impurityelement at a low concentration.

As the polysilicon film 372, a semiconductor film having a crystalstructure is used, which is formed in such a manner that an amorphoussilicon film is formed by a sputtering method, an LPCVD method, a plasmaCVD method, or the like, and then the amorphous silicon film iscrystallized by crystallization treatment (a laser crystallizationmethod, a thermal crystallization method, a thermal crystallizationmethod using a catalyst such as nickel, or the like).

The transistors 380 a and 370 a each include the polysilicon film as asemiconductor layer. A transistor including a polysilicon film can havea higher field-effect mobility and thus have higher on-state currentthan a transistor including amorphous silicon. Consequently, a circuitcapable of high-speed operation can be obtained. Furthermore, the areaoccupied by a circuit portion can be reduced.

The transistors 380 a and 370 a are covered with an insulating layer 317and an insulating layer 319. Note that the insulating layers 317 and 319can be regarded as the components of the transistors 380 a and 370 a.

The liquid crystal element 307 a is a liquid crystal element having afringe field switching (FFS) mode. The liquid crystal element 307 aincludes a conductive layer 351, a conductive film layer 352, and aliquid crystal 349. Alignment of the liquid crystal 349 can becontrolled with an electric field generated between the conductivelayers 351 and 352. The conductive layer 351 can serve as a pixelelectrode. The conductive layer 352 can serve as a common electrode.

When a conductive material that transmits visible light is used for theconductive layers 351 and 352, the liquid crystal display device 200 canserve as a transmissive liquid crystal display device. When a conductivematerial that reflects visible light is used for the conductive layer351 and a conductive material that transmits visible light is used forthe conductive layer 352, the liquid crystal display device 200 canserve as a reflective liquid crystal display device.

The conductive layer 351 serving as a pixel electrode is electricallyconnected to a source or a drain of the transistor 370 a. Here, theconductive layer 351 is electrically connected to the conductive layer374 b.

The conductive layer 352 has a comb-like top surface shape or a topsurface shape provided with a slit (a top surface shape is also referredto as a planar surface shape). An insulating layer 353 is providedbetween the conductive layers 351 and 352. The conductive layer 351partly overlaps with the conductive layer 352 with the insulating layer353 interposed therebetween. In a region where a coloring film 341overlaps with the conductive layer 351, there is a portion where theconductive layer 352 is not provided over the conductive layer 351.

The connection portion 305 a is electrically connected to an externalinput terminal through which a signal (e.g., a video signal, a clocksignal, a start signal, and a reset signal) or a potential from theoutside is transmitted to the gate line driver circuit 202. An examplein which the FPC 369 is provided as an external input terminal is shownhere.

The connection portion 305 a includes a conductive layer 331 over theinsulating layer 313, a conductive layer 333 over the conductive layer331, and a conductive layer 335 over the conductive layer 333. Theconductive layer 331 is electrically connected to the conductive layer335 via the conductive layer 333. The conductive layer 335 iselectrically connected to the FPC 369 via a connector 367.

The conductive layer 331 can be formed using the same material and thesame step as those of the conductive layer 374 a and the conductivelayer 374 b included in the transistors 380 a and 370 a. The conductivelayer 333 can be formed using the same material and the same step asthose of the conductive layer 351 included in the liquid crystal element307 a. The conductive layer 335 can be formed using the same materialand the same step as those of the conductive layer 352 included in theliquid crystal element 307 a. It is preferable to form the conductivelayers included in the connection portion 305 a using the same materialsand the same steps as an electrode or a wiring used for a displayportion or a driver circuit portion in such a manner because an increasein number of steps can be prevented.

A substrate 361 is provided with the coloring film 341, a light-blockingfilm 343, and an insulating layer 345. FIG. 8B illustrates an example inwhich the substrate 361 has a smaller thickness than the substrate 311;however, one embodiment of the present invention is not limited to thisexample. One of the substrates 361 and 311 may be thinner than theother, or the substrates 361 and 311 may have the same thickness. It ispreferable to make the substrate on the display surface side (the sidenear a sensing target) thin because the sensitivity of a sensor elementcan be increased.

The coloring film 341 partly overlaps with the liquid crystal element307 a. The light-blocking film 343 partly overlaps with at least one ofthe transistors 380 a and 370 a.

The insulating layer 345 preferably has a function of an overcoatpreventing impurities contained in the coloring film 341, thelight-blocking film 343, and the like from diffusing into the liquidcrystal 349. The insulating layer 345 is not necessarily provided.

Note that alignment films may be provided on sides of the substrates 311and 361 which are in contact with the liquid crystal 349. The alignmentfilm can control the alignment of the liquid crystal 349. For example,in FIG. 8B, an alignment film may be formed to cover the conductivelayer 352 or may be formed between the insulating layer 345 and theliquid crystal 349. The insulating layer 345 may serve as an alignmentfilm and an overcoat.

The liquid crystal display device 200 includes a spacer 347. The spacer347 has a function of preventing the distance between the substrate 311and the substrate 361 from being shorter than or equal to a certaindistance.

FIG. 8B illustrates an example in which the spacer 347 is provided overthe insulating layer 353 and the conductive layer 352; however, oneembodiment of the present invention is not limited thereto. The spacer347 may be provided on the substrate 311 side or on the substrate 361side. For example, the spacer 347 may be formed on the insulating layer345. Moreover, although FIG. 8B illustrates an example in which thespacer 347 is in contact with the insulating layers 353 and 345, thespacer 347 is not necessarily in contact with a component provided onthe substrate 311 side or on the substrate 361 side.

A particulate spacer may be used as the spacer 347. Although a materialsuch as silica can be used for the particulate spacer, an elasticmaterial such as a resin or rubber is preferably used. In that case, theparticulate spacer may be vertically crushed.

The substrates 311 and 361 are attached to each other with a bondinglayer 365. A region surrounded by the substrate 311, the substrate 361,and the bonding layer 365 is filled with the liquid crystal 349.

Note that when the liquid crystal display device 200 serves as atransmissive liquid crystal display device, two polarizing plates areprovided so that a display portion is sandwiched between the twopolarizing plates. Light from a backlight provided outside thepolarizing plate enters through the polarizing plate. At this time, thealignment of the liquid crystal 349 is controlled with a voltage appliedbetween the conductive layers 351 and 352, whereby optical modulation oflight can be controlled. In other words, the intensity of light emittedthrough the polarizing plate can be controlled. Light excluding light ina particular wavelength range is absorbed by the coloring film 341, sothat red, blue, or green light is emitted.

In addition to the polarizing plate, a circularly polarizing plate canbe used, for example. As the circularly polarizing plate, for example, astack including a linear polarizing plate and a quarter-wave retardationplate can be used. With the circularly polarizing plate, the viewingangle dependence of display of the liquid crystal display device can bereduced.

Note that the liquid crystal element 307 a is an element using an FFSmode here; however, one embodiment of the present invention is notlimited thereto, and a liquid crystal element using any of a variety ofmodes can be used. For example, a liquid crystal element using avertical alignment (VA) mode, a twisted nematic (TN) mode, an in-planeswitching (IPS) mode, an axially symmetric aligned micro-cell (ASM)mode, an optically compensated birefringence (OCB) mode, a ferroelectricliquid crystal (FLC) mode, an antiferroelectric liquid crystal (AFLC)mode, a vertical alignment in-plane-switching (VA-IPS) mode, or the likecan be used.

Furthermore, a normally black liquid crystal display device, forexample, a transmissive liquid crystal display device using a verticalalignment (VA) mode, may be used as the liquid crystal display device200. As a vertical alignment mode, a multi-domain vertical alignment(MVA) mode, a patterned vertical alignment (PVA) mode, or an ASV modecan be employed, for example.

Note that the liquid crystal element is an element that controlstransmission or non-transmission of light by utilizing an opticalmodulation action of liquid crystal. Note that optical modulation actionof a liquid crystal is controlled by an electric field applied to theliquid crystal (including a horizontal electric field, a verticalelectric field, and an oblique electric field). As the liquid crystalused for the liquid crystal element, thermotropic liquid crystal,low-molecular liquid crystal, high-molecular liquid crystal, polymerdispersed liquid crystal (PDLC), ferroelectric liquid crystal,anti-ferroelectric liquid crystal, or the like can be used. Such aliquid crystal material exhibits a blue phase, a cholesteric phase, asmectic phase, a cubic phase, a chiral nematic phase, an isotropicphase, or the like depending on conditions.

As the liquid crystal material, a positive liquid crystal or a negativeliquid crystal may be used, and an appropriate liquid crystal materialcan be used depending on the mode and design to be used.

A substrate with which a sensing target, such as a finger or a stylus,is to be in contact may be provided above the substrate 361. In thatcase, a polarizing plate or a circularly polarizing plate is preferablyprovided between the substrate 361 and the above substrate. In thatcase, a protective layer (such as a ceramic coat) is preferably providedover the above substrate. The protective layer can be formed using aninorganic insulating material such as silicon oxide, aluminum oxide,yttrium oxide, or yttria-stabilized zirconia (YSZ). Alternatively,tempered glass may be used for the substrate. Physical or chemicalprocessing by an ion exchange method, a wind tempering method, or thelike is performed on the tempered glass, so that compressive stress isapplied on the surface.

FIG. 9 is a cross-sectional view of two adjacent subpixels. Twosubpixels illustrated in FIG. 9 are included in respective pixels.

In FIG. 9, proximity, touch, or the like of a sensing target can besensed by utilizing capacitance formed between the conductive layer 352of a liquid crystal element 307 b included in a subpixel and a wiring352 a and capacitance formed between the conductive layer 352 of theliquid crystal element 307 a included in an adjacent subpixel and thewiring 352 a. The wiring 352 a is positioned between the two conductivelayers 352. That is, in the liquid crystal display device of oneembodiment of the present invention, the conductive layer 352 serves asa common electrode of the liquid crystal element and an electrode of thesensor element.

As described above, an electrode included in the liquid crystal elementalso serves as an electrode included in the sensor element in the liquidcrystal display device of one embodiment of the present invention; thus,the manufacturing process can be simplified and the manufacturing costcan be reduced. In addition, the thickness and weight of the liquidcrystal display device can be reduced.

When the capacitance between the electrode of the sensor element and asignal line is too large, the time constant of the electrode of thesensor element becomes too large in some cases. Thus, an insulatinglayer having a planarizing function is preferably provided between theelectrode of the sensor element and the transistors to reduce thecapacitance between the electrode of the sensor element and the signalline. For example, in FIG. 9, as the insulating layer having aplanarizing function, the insulating layer 319 is provided. With theinsulating layer 319, the capacitance between the conductive layer 352and the signal line can be small. Accordingly, the time constant of theelectrode of the sensor element can be small. As described above, thesmaller the time constant of the electrode of the sensor element is, thehigher the sensitivity and the sensing accuracy are.

For example, the time constant of the electrode of the sensor element isgreater than 0 seconds and smaller than or equal to 1×10⁻⁴ seconds,preferably greater than 0 seconds and smaller than or equal to 5×10⁻⁵seconds, more preferably greater than 0 seconds and smaller than orequal to 5×10⁻⁶ seconds, more preferably greater than 0 seconds andsmaller than or equal to 5×10⁻⁷ seconds, more preferably greater than 0seconds and smaller than or equal to 2×10⁻⁷ seconds. In particular, whenthe time constant is smaller than or equal to 1×10⁻⁶ seconds, highsensitivity can be achieved while the influence of noise is reduced.

Next, the details of the materials and the like that can be used forcomponents of the liquid crystal display device of this embodiment aredescribed.

<<Substrate>>

There is no particular limitation on a material and the like of thesubstrates included in the liquid crystal display device 200 as long asthe material has heat resistance high enough to withstand at least heattreatment performed later. For example, a glass substrate, a ceramicsubstrate, a quartz substrate, a sapphire substrate, or the like may beused as the substrates. Alternatively, a single crystal semiconductorsubstrate or a polycrystalline semiconductor substrate made of siliconor silicon carbide, a compound semiconductor substrate made of silicongermanium or the like, an SOI substrate, or the like may be used. Stillalternatively, any of these substrates provided with a semiconductorelement may be used as the substrates 311 and 361. In the case where aglass substrate is used as the substrates 311 and 361, a glass substratehaving any of the following sizes can be used: the 6th generation (1500mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8th generation(2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm), and the 10thgeneration (2950 mm×3400 mm). Thus, a large-sized display device can bemanufactured. Alternatively, a flexible substrate may be used as thesubstrates 311 and 361, and the transistor, the capacitor, and the likemay be formed directly on the flexible substrate.

The weight and thickness of the liquid crystal display device can bereduced by using a thin substrate. Furthermore, a flexible liquidcrystal display device can be obtained by using a substrate that is thinenough to have flexibility.

Other than the above, a transistor can be formed using varioussubstrates as the substrates 311 and 361. The type of a substrate is notlimited to a certain type. Examples of the substrate include a plasticsubstrate, a metal substrate, a stainless steel substrate, a substrateincluding stainless steel foil, a tungsten substrate, a substrateincluding tungsten foil, a flexible substrate, an attachment film, paperincluding a fibrous material, and a base film. As an example of a glasssubstrate, a barium borosilicate glass substrate, an aluminoborosilicateglass substrate, a soda lime glass substrate, or the like can be given.Examples of a flexible substrate include a flexible synthetic resin suchas plastics typified by polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), and polyether sulfone (PES), and acrylic. Examples ofan attachment film are attachment films formed using polypropylene,polyester, polyvinyl fluoride, polyvinyl chloride, and the like.Examples of the material for the base film include polyester, polyamide,polyimide, inorganic vapor deposition film, and paper. Specifically, theuse of semiconductor substrates, single crystal substrates, SOIsubstrates, or the like enables the manufacture of small-sizedtransistors with a small variation in characteristics, size, shape, orthe like and with high current capability. A circuit using suchtransistors achieves lower power consumption of the circuit or higherintegration of the circuit.

Note that a transistor may be formed using one substrate, and then thetransistor may be transferred to another substrate. Examples of asubstrate to which a transistor is transferred include, in addition tothe above substrate over which the transistor can be formed, a papersubstrate, a cellophane substrate, a stone substrate, a wood substrate,a cloth substrate (including a natural fiber (e.g., silk, cotton, orhemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), aregenerated fiber (e.g., acetate, cupra, rayon, or regeneratedpolyester), and the like), a leather substrate, and a rubber substrate.When such a substrate is used, a transistor with excellent properties ora transistor with low power consumption can be formed, a device withhigh durability or high heat resistance can be provided, or reduction inweight or thickness can be achieved.

<<Transistor Using Polysilicon Film>>

The structure of the transistors in the liquid crystal display device ofone embodiment of the present invention is not particularly limited. Forexample, a planar transistor, a staggered transistor, or an invertedstaggered transistor may be used. A top-gate transistor or a bottom-gatetransistor may be used. Gate electrodes may be provided above and belowa channel.

Transistors including polysilicon films can form various functionalcircuits, such as a shift register circuit, a level shifter circuit, abuffer circuit, and a sampling circuit, because of their highfield-effect mobility.

<<Insulating Layer>>

An organic insulating material or an inorganic insulating material canbe used as an insulating material that can be used for the insulatinglayer, the overcoat, the spacer, or the like included in the liquidcrystal display device. Examples of a resin include an acrylic resin, anepoxy resin, a polyimide resin, a polyamide resin, a polyamide-imideresin, a siloxane resin, a benzocyclobutene-based resin, and a phenolresin. Examples of an inorganic insulating layer include a silicon oxidefilm, a silicon oxynitride film, a silicon nitride oxide film, a siliconnitride film, an aluminum oxide film, a hafnium oxide film, an yttriumoxide film, a zirconium oxide film, a gallium oxide film, a tantalumoxide film, a magnesium oxide film, a lanthanum oxide film, a ceriumoxide film, and a neodymium oxide film.

<<Conductive Layer>>

For the conductive layer such as the gate, the source, and the drain ofa transistor and the wiring, the electrode, and the like of the liquidcrystal display device, a single-layer structure or a stacked structureusing any of metals such as aluminum, titanium, chromium, nickel,copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten,or an alloy containing any of these metals as its main component can beused. For example, a two-layer structure in which a titanium film isstacked over an aluminum film, a two-layer structure in which a titaniumfilm is stacked over a tungsten film, a two-layer structure in which acopper film is stacked over a molybdenum film, a two-layer structure inwhich a copper film is stacked over an alloy film containing molybdenumand tungsten, a two-layer structure in which a copper film is stackedover a copper-magnesium-aluminum alloy film, a three-layer structure inwhich a titanium film or a titanium nitride film, an aluminum film or acopper film, and a titanium film or a titanium nitride film are stackedin this order, a three-layer structure in which a molybdenum film or amolybdenum nitride film, an aluminum film or a copper film, and amolybdenum film or a molybdenum nitride film are stacked in this order,and the like can be given. For example, in the case where the conductivelayer has a three-layer structure, it is preferable that each of thefirst and third layers be a film formed of titanium, titanium nitride,molybdenum, tungsten, an alloy containing molybdenum and tungsten, analloy containing molybdenum and zirconium, or molybdenum nitride, andthat the second layer be a film formed of a low-resistance material suchas copper, aluminum, gold, silver, or an alloy containing copper andmanganese. A light-transmitting conductive material such as indium tinoxide, indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, indium zinc oxide, or indiumtin oxide to which silicon oxide is added may be used.

Note that the conductive layer may be formed using a method forcontrolling the resistivity of an oxide semiconductor.

The structure and method described in this embodiment can be implementedby being combined as appropriate with any of the other structures andmethods described in the other embodiments.

Embodiment 2

In this embodiment, the structure of a display device of one embodimentof the present invention will be described with reference to FIGS. 10Ato 10D, FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13A and 13B, FIGS.14A and 14B, FIGS. 15A to 15C, FIGS. 16A to 16C, FIG. 17, FIGS. 18A and18B, FIG. 19, FIGS. 20A to 20D, FIGS. 21A to 21C, FIGS. 22A and 22B,FIGS. 23A-1, 23A-2, 23B-1, 23B-2, 23C-1, 23C-2, 23D-1, 23D-2, 23E-1,23E-2, 23F-1, and 23F-2, and FIGS. 24A to 24C.

FIGS. 10A to 10D illustrate the structure of the display device of oneembodiment of the present invention. FIG. 10A is a projection view of apixel, and FIG. 10B is an exploded view illustrating part of thestructure of the pixel in FIG. 10A. FIG. 10C is a cross-sectional viewthat is taken along line Y1-Y2 in FIG. 10A and illustrates part of thestructure of the pixel. FIG. 10D is a top view of the pixel in FIG. 10A.

FIGS. 11A and 11B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 11A is a cross-sectional viewof the pixel taken along line Y1-Y2 in FIG. 10A. FIG. 11B is across-sectional view illustrating part of the structure of the pixel inFIG. 11A.

FIGS. 12A and 12B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 12A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 12B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 12A.

FIGS. 13A and 13B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 13A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 13B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 13A.

FIGS. 14A and 14B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 14A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 14B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 14A.

FIGS. 15A to 15C illustrate the structure of the display device of oneembodiment of the present invention. FIG. 15A is a top view of thedisplay device. FIG. 15B is a top view illustrating part of the pixel ofthe display device in FIG. 15A. FIG. 15C is a schematic viewillustrating a cross-sectional structure of the display device in FIG.15A.

FIGS. 16A to 16C and FIG. 17 are cross-sectional views illustrating thestructure of the display device. FIG. 16A is a cross-sectional viewtaken along line X1-X2 and line X3-X4 in FIG. 15A, and line X5-X6 inFIG. 15B. FIGS. 16B and 16C each illustrate part of FIG. 16A.

FIG. 17 is a cross-sectional view taken along line X7-X8 in FIG. 15B andline X9-X10 in FIG. 15A.

FIGS. 18A and 18B are bottom views each illustrating part of a pixelthat can be used for the display device illustrated in FIG. 15A.

FIG. 19 is a circuit diagram illustrating the configuration of a pixelcircuit included in a display device of one embodiment of the presentinvention.

Note that in this specification, an integral variable of 1 or more maybe used for reference numerals. For example, “(p)” where p is anintegral value of 1 or more may be used for part of a reference numeralthat specifies any one of components (up top components). For anotherexample, “(m,n)” where m and n are each an integral value of 1 or moremay be used for part of a reference numeral that specifies any one ofcomponents (up to m×n components).

<Structural Example 1 of Display Device>

A display device 700 described in this embodiment includes a pixel702(i,j) (see FIG. 15A).

<<Structural Example 1 of Pixel>>

The pixel 702(i,j) includes a functional layer 520, a first displayelement 750(i,j), and a second display element 550(i,j) (see FIG. 15A).

The functional layer 520 includes a pixel circuit 530(i,j). Thefunctional layer 520 includes a region positioned between the firstdisplay element 750(i,j) and the second display element 550(i,j).

The pixel circuit 530(i,j) is electrically connected to the firstdisplay element 750(i,j) and the second display element 550(i,j).

<<Structural Example 1 of First Display Element 750(i,j)>>

The first display element 750(i, j) includes a first electrode 751(i,j), a second electrode 752, a layer 753 containing a liquid crystalmaterial, and a reflective film 751B (see FIG. 10B and FIG. 11B). Thefirst display element 750(i,j) has a function of controlling theintensity of light reflected by the reflective film 751B.

The second electrode 752 is provided such that an electric field in thedirection intersecting the thickness direction of the layer 753containing a liquid crystal material is formed between the secondelectrode 752 and the first electrode 751(i,j) (see FIG. 10B and FIG.11A). For example, the second electrode 752 can have a comb-like shape.In this manner, an electric field in the direction intersecting thethickness direction of the layer 753 containing a liquid crystalmaterial can be formed between the second electrode 752 and the firstelectrode 751(i,j). Alternatively, a display element operating in aVA-IPS mode can be used as the first display element.

FIG. 22B is an external view of a matrix of the second electrodes 752with a comb-like shape.

The reflective film 751B has a shape that does not block light emittedfrom the second display element 550(i,j). For example, the reflectivefilm 751B can have a shape including a region 751H where light is notblocked.

<<Structural Example 1 of Second Display Element 550(i,j)>>

The second display element 550(i,j) has a function of emitting light andis provided such that display using the second display element can beseen from part of a region where display using the first display element750(i,j) can be seen (see FIG. 11A).

With such a structure, display can be performed by controlling theintensity of light reflected by the reflective film with the use of thefirst display element. Furthermore, display using the first displayelement can be complemented using the second display element.Consequently, a novel display device with high convenience or highreliability can be provided.

<<Structural Example 2 of Pixel>>

In the display device 700 described in this embodiment, the pixel702(i,j) includes an optical element 560 and a covering film 565.

<<Structural Example 1 of Optical Element>>

The optical element 560 has a light-transmitting property and includes afirst region 560A, a second region 560B, and a third region 560C (seeFIGS. 10B and 10C and FIG. 11B).

The first region 560A includes a region to which light is supplied. Forexample, the first region 560A receives light from the second displayelement 550(i,j).

The second region 560B includes a region in contact with the coveringfilm 565.

The third region 560C has a function of allowing part of light to beextracted and has an area smaller than or equal to the area of theregion of the first region 560A to which light is supplied.

<<Structural Example of Covering Film>>

The covering film 565 has light reflectivity and has a function ofreflecting part of light and supplying it to the third region 560C. Forexample, the covering film 565 can reflect light emitted from the seconddisplay element 550(i,j) toward the third region 560C. Specifically,part of light incident on the optical element 560 through the firstregion 560A can be reflected by the covering film 565 in contact withthe second region 560B and extracted from the third region 560C, asshown by a solid arrow (see FIG. 11B).

<<Structural Example 2 of First Display Element 750(i,j)>>

The reflective film 751B has a shape that does not block light extractedfrom the third region 560C.

With such a structure, display can be performed by controlling theintensity of light reflected by the reflective film with the use of thefirst display element. Alternatively, display using the first displayelement can be complemented using the second display element.Alternatively, the light supplied to the first region can be efficientlyemitted from the third region. Alternatively, the light supplied to thefirst region can be gathered and emitted from the third region. Forexample, when a light-emitting element is used as the second displayelement, the area of the light-emitting element can be larger than thatof the third region. Alternatively, light supplied from thelight-emitting element having an area larger than the area of the thirdregion can be gathered in the third region. Alternatively, the densityof a current flowing through the light-emitting element can be decreasedwhile the intensity of light emitted from the third region ismaintained. Alternatively, the reliability of the light-emitting elementcan be increased. For example, an organic EL element or a light-emittingdiode can be used as the light-emitting element. Consequently, a noveldisplay device with high convenience or high reliability can beprovided.

<<Structural Example 3 of Pixel>>

The pixel 702(i,j) includes part of the functional layer 520, a firstdisplay element 750(i,j), and a second display element 550(i,j) (seeFIG. 15C).

<<Functional Layer 520>>

The functional layer 520 includes a first conductive layer, a secondconductive layer, an insulating film 501C, and the pixel circuit530(i,j). The functional layer 520 includes the optical element 560 andthe covering film 565 (see FIG. 11A and FIG. 16A). The pixel circuit530(i,j) includes a transistor M, for example.

The functional layer 520 includes a region positioned between the firstdisplay element 750(i,j) and the second display element 550(i,j) (seeFIG. 16C). The region positioned between the first display element750(i,j) and the second display element 550(i,j) has a thickness of lessthan 30 μm, preferably less than 10 μm, further preferably less than 5μm.

In this manner, the second display element 550(i,j) can be close to thefirst display element 750(i,j). Parallax between display using the firstdisplay element 750(i,j) and display using the second display element550(i,j) can be reduced. Display using an adjacent pixel (e.g., thepixel 702(i,j+1)) can be inhibited from being disturbed by display usingthe second display element 550(i,j). The color of display using anadjacent pixel (e.g., the pixel 702(i,j+1)) and the color of displayusing the second display element 550(i,j) can be inhibited from beingmixed. The attenuation of light emitted by the second display element550(i,j) can be inhibited. The weight of the display device can bereduced. The thickness of the display device can be reduced. The displaydevice is easily bendable.

The functional layer 520 includes an insulating film 528, an insulatingfilm 521A, an insulating film 521B, an insulating film 518, and aninsulating film 516.

<<Pixel Circuit>>

The pixel circuit 530(i,j) has a function of driving the first displayelement 750(i,j) and the second display element 550(i,j) (see FIG. 19).

Thus, the first display element and the second display element thatdisplays an image by a method different from that of the first displayelement can be driven using pixel circuits that can be formed in thesame process. Specifically, a reflective display element is used as thefirst display element, whereby power consumption can be reduced. Animage with high contrast can be favorably displayed in an environmentwith bright external light. An image can be favorably displayed in adark environment with the use of the second display element which emitslight. With the insulating film, impurity diffusion between the firstdisplay element and the second display element or between the firstdisplay element and the pixel circuit can be inhibited. Consequently, anovel display device with high convenience or high reliability can beprovided.

A switch, a transistor, a diode, a resistor, an inductor, a capacitor,or the like can be used in the pixel circuit 530(i,j).

For example, one or a plurality of transistors can be used as a switch.Alternatively, a plurality of transistors connected in parallel, inseries, or in combination of parallel connection and series connectioncan be used as a switch.

For example, the pixel circuit 530(i,j) is electrically connected to asignal line S1(j), a signal line S2(j), a scan line G1(i), a scan lineG2(i), a wiring CSCOM, and a wiring ANO (see FIG. 19). Although notillustrated, a conductive layer 512A is electrically connected to thesignal line S1(j).

The pixel circuit 530(i,j) includes a switch SW1 and a capacitor C11(see FIG. 19).

The pixel circuit 530(i,j) includes a switch SW2, a transistor M, and acapacitor C12.

For example, a transistor including a gate electrode electricallyconnected to the scan line G1(i) and a first electrode electricallyconnected to the signal line S1(j) can be used as the switch SW1.

The capacitor C11 includes a first electrode electrically connected to asecond electrode of the transistor used as the switch SW1 and a secondelectrode electrically connected to the wiring CSCOM.

For example, a transistor including a gate electrode electricallyconnected to the scan line G2(i) and a first electrode electricallyconnected to the signal line S2(j) can be used as the switch SW2.

The transistor M includes a gate electrode electrically connected to asecond electrode of the transistor used as the switch SW2 and a firstelectrode electrically connected to the wiring ANO.

Note that a transistor including a conductive layer provided such that asemiconductor film is positioned between a gate electrode and theconductive layer can be used as the transistor M. For example, as theconductive layer, a conductive layer electrically connected to a wiringthat can supply the same potential as that of the gate electrode of thetransistor M can be used.

The capacitor C12 includes a first electrode electrically connected tothe second electrode of the transistor used as the switch SW2 and asecond electrode electrically connected to the first electrode of thetransistor M.

A first electrode of the first display element 750(i,j) is electricallyconnected to the second electrode of the transistor used as the switchSW1. The second electrode 752 of the first display element 750(i,j) iselectrically connected to a wiring VCOM1. This enables the first displayelement 750 to be driven.

The electrode 551(i,j) and the electrode 552 of the second displayelement 550(i,j) are electrically connected to a second electrode of thetransistor M and a conductive layer VCOM2, respectively. This enablesthe second display element 550(i,j) to be driven.

<<Insulating Film 501C>>

The insulating film 501C includes a region positioned between the firstconductive layer and the second conductive layer and has an opening 591A(see FIG. 17).

<<First Conductive Layer>>

The first conductive layer is electrically connected to the firstdisplay element 750(i,j). Specifically, the first conductive layer iselectrically connected to the first electrode 751(i,j) of the firstdisplay element 750(i,j). The first electrode 751(i,j) can be used asthe first conductive layer.

<<Second Conductive Layer>>

The second conductive layer includes a region overlapping with the firstconductive layer. The second conductive layer is electrically connectedto the first conductive layer through the opening 591A. For example, aconductive layer 512B can be used as the second conductive layer.

Note that the first conductive layer electrically connected to thesecond conductive layer in the opening 591A formed in the insulatingfilm 501C can be referred to as a through electrode.

The second conductive layer is electrically connected to the pixelcircuit 530(i,j). For example, a conductive layer that functions as asource electrode or a drain electrode of a transistor used as a switchSW1 of the pixel circuit 530(i,j) can be used as the second conductivelayer.

<<Structural Example 2 of Second Display Element 550(i,j)>>

The second display element 550(i,j) is electrically connected to thepixel circuit 530(i,j) (see FIG. 16A and FIG. 19). The second displayelement 550(i,j) has a function of emitting light toward the functionallayer 520. The second display element 550(i,j) has a function ofemitting light toward the insulating film 501C or an opening formed inthe insulating film 501C, for example.

The second display element 550(i,j) is provided such that display usingthe second display element 550(i,j) can be seen from part of a regionwhere display using the first display element 750(i,j) can be seen. Forexample, dashed arrows shown in FIG. 17 denote the directions in whichexternal light is incident on and reflected by the first display element750(i,j) that displays image data by controlling the intensity ofexternal light reflection. In addition, a solid arrow shown in FIG. 16Adenotes the direction in which the second display element 550(i,j) emitslight to part of the region where display using the first displayelement 750(i,j) can be seen.

Accordingly, display using the second display element can be seen frompart of the region where display using the first display element can beseen. Alternatively, users can see display without changing the attitudeor the like of the display device. Alternatively, an object colorexpressed by light reflected by the first display element and a lightsource color expressed by light emitted from the second display elementcan be mixed. Alternatively, an object color and a light source colorcan be used to display an image like a painting. Thus, a novel displaydevice with high convenience or high reliability can be provided.

For example, the second display element 550(i,j) includes the electrode551(i,j), the electrode 552, and the layer 553(j) containing alight-emitting material (see FIG. 16A).

The electrode 552 includes a region overlapping with the electrode551(i,j).

The layer 553(j) containing a light-emitting material includes a regionpositioned between the electrode 551(i,j) and the electrode 552.

The electrode 551(i,j) is electrically connected to the pixel circuit530(i,j) at a connection portion 522. The electrode 552 is electricallyconnected to the conductive layer VCOM2 (see FIG. 16A and FIG. 19).

<<Insulating Films 521, 528, 518, and 516>>

An insulating film 521 includes a region positioned between the pixelcircuit 530(i,j) and the second display element 550(i,j).

For example, a laminated film can be used as the insulating film 521.For example, a stack including the insulating film 521A, the insulatingfilm 521B, and an insulating film 521C can be used as the insulatingfilm 521.

The insulating film 528 includes a region positioned between theinsulating film 521 and the substrate 570 and has an opening in a regionoverlapping with the second display element 550(i,j). The insulatingfilm 528 that is along the edge of the electrode 551(i,j) can avoid ashort circuit between the electrode 551(i,j) and the electrode 552.

Note that a single-layer film or a stacked-layer film can be used forthe insulating film 518. For example, an insulating film 518A and aninsulating film 518B can be used for the insulating film 518.Alternatively, for example, an insulating film 518A1 and an insulatingfilm 518A2 can be used for the insulating film 518.

The insulating film 518 includes a region positioned between theinsulating film 521 and the pixel circuit 530(i,j).

The insulating film 516 includes a region positioned between theinsulating film 518 and the pixel circuit 530(i,j).

Furthermore, the display device 700 can include an insulating film 501B.The insulating film 501B has an opening 592B (see FIG. 16A).

The opening 592B includes a region overlapping with a conductive layer511B.

<Structural Example 2 of Display Device>

The display device 700 described in this embodiment includes a displayregion 231 (see FIGS. 15A to 15C).

<<Display Region 231>>

Although not specifically illustrated, the display region 231 includesone group of pixels 702(i,1) to 702(i,n), another group of pixels702(1,j) to 702(m,j), a scan line G1(i), and a signal line S1(j). As anexample, FIGS. 15A to 15C illustrate the pixel 702(i,j). The displayregion 231 includes the scan line G2(i), the wiring CSCOM, the wiringANO, and the signal line S2(j) (see FIGS. 15A to 15C and FIG. 19). Notethat i is an integer greater than or equal to 1 and less than or equalto m, j is an integer greater than or equal to 1 and less than or equalto n, and each of m and n is an integer greater than or equal to 1.

The one group of pixels 702(i,1) to 702(i,n) include the pixel 702(i,j)and are arranged in the row direction (the direction indicated by thearrow R1 in the drawing).

The another group of pixels 702(1,j) to 702(m,j) include the pixel702(i,j) and are arranged in the column direction (the directionindicated by the arrow C1 in the drawing) that intersects the rowdirection.

The scan line G1(i) and the scan line G2(i) are electrically connectedto the group of pixels 702(1,1) to 702(i,n) arranged in the rowdirection.

The signal line S1(i) and the signal line S2(j) are electricallyconnected to the another group of pixels 702(1,j) to 702(m,j) arrangedin the column direction.

<Structural Example 3 of Display Device>

The display device 700 described in this embodiment can include aplurality of pixels having functions of representing colors withdifferent hues. Furthermore, colors with hues that cannot be representedby the plurality of pixels capable of representing colors with differenthues can be represented by additive color mixing with the use of thepixels.

Note that when a plurality of pixels capable of representing colors withdifferent hues are used for color mixture, each of the pixels can bereferred to as a subpixel. In addition, a set of subpixels can bereferred to as a pixel. Specifically, the pixel 702(i,j) can be referredto as a subpixel, and the pixel 702(i,j), a pixel 702(i,j+1), and apixel 702(i,j+2) can be collectively referred to as a pixel 703(i,k)(see FIG. 22A).

For example, a subpixel that represents blue, a subpixel that representsgreen, and a subpixel that represents red can be collectively used asthe pixel 703(i,k).

Alternatively, for example, a subpixel that represents cyan, a subpixelthat represents magenta, and a subpixel that represents yellow can becollectively used as the pixel 703(i,k).

Alternatively, for example, the above set to which a subpixel thatrepresents white is added can be used as the pixel.

Alternatively, for example, a set of the following subpixels can be usedas the pixel 703(i,k): a subpixel including the first display element750(i,j) that represents cyan and the second display element 550(i,j)that represents blue; a subpixel including a first display element750(i,j+1) that represents yellow and a second display element550(i,j+1) that represents green; and a subpixel including a firstdisplay element 750(i,j+2) that represents magenta and a second displayelement 550(i,j+2) that represents red. This allows bright display usingthe first display elements 750(i,j) to 750(i,j+2) or clear display usingthe second display elements 550(i,j) to 550(i,j+2).

<Structural Example 4 of Display Device>

The display device 700 described in this embodiment can include a drivercircuit GD or a driver circuit SD (see FIG. 15A).

<<Driver Circuit GD>>

The driver circuit GD has a function of supplying a selection signal onthe basis of control data.

For example, the driver circuit GD has a function of supplying aselection signal to one scan line at a frequency of 30 Hz or higher,preferably 60 Hz or higher, on the basis of control data. Accordingly,moving images can be smoothly displayed.

For example, the driver circuit GD has a function of supplying aselection signal to one scan line at a frequency of lower than 30 Hz,preferably lower than 1 Hz, more preferably less than once per minute,on the basis of control data. Accordingly, a still image can bedisplayed with reduced flickering.

A display device can include a plurality of driver circuits. Forexample, a display device 700B includes a driver circuit GDA and adriver circuit GDB (see FIGS. 15A to 15C).

For example, in the case where a plurality of driver circuits areprovided, the driver circuits GDA and GDB may supply the selectionsignals at different frequencies. Specifically, the selection signal canbe supplied at a higher frequency to a region on which moving images aredisplayed than to a region on which a still image is displayed.Accordingly, a still image can be displayed in a region with reducedflickering, and moving images can be smoothly displayed in anotherregion.

<<Driver Circuit SD>>

Although not illustrated, the driver circuit SD includes a drivercircuit SD1 and a driver circuit SD2. The driver circuit SD1 has afunction of supplying an image signal on the basis of data V11. Thedriver circuit SD2 has a function of supplying an image signal on thebasis of data V12 (see FIGS. 15A to 15C).

The driver circuit SD1 or the driver circuit SD2 has a function ofgenerating an image signal and a function of supplying the image signalto a pixel circuit electrically connected to a display element.Specifically, the driver circuit SD1 or the driver circuit SD2 has afunction of generating a signal whose polarity is inverted. Thus, forexample, a liquid crystal display element can be driven.

For example, any of a variety of sequential circuits, such as a shiftregister, can be used as the driver circuit SD.

For example, an integrated circuit in which the driver circuit SD1 andthe driver circuit SD2 are integrated can be used as the driver circuitSD. Specifically, an integrated circuit formed on a silicon substratecan be used as the driver circuit SD.

An integrated circuit can be mounted on a terminal by a chip on glass(COG) method or a chip on film (COF) method, for example. Specifically,an anisotropic conductive layer can be used to mount an integratedcircuit on the terminal.

<Structural Example 5 of Display Device>

Moreover, the display device 700 described in this embodiment includes afunctional layer 720, a terminal 519B, the substrate 570, a substrate770, a bonding layer 505, a sealing material 705, a structure body KB1,a functional film 770P, a functional film 770D, and the like (see FIG.16A and FIG. 17).

<<Functional Layer 720>>

The display device described in this embodiment includes the functionallayer 720. The functional layer 720 includes a region positioned betweenthe substrate 770 and the insulating film 501C. The functional layer 720includes a light-blocking film BM, an insulating film 771, and acoloring film CF1 (see FIG. 16A and FIG. 17).

The light-blocking film BM has an opening in a region overlapping withthe first display element 750(i,j).

The coloring film CF1 includes a region positioned between the substrate770 and the first display element 750(i,j).

The insulating film 771 includes a region between the coloring film CF1and the layer 753 containing a liquid crystal material and a regionbetween the light-blocking film BM and the layer 753 containing a liquidcrystal material. The insulating film 771 can reduce unevenness due tothe thickness of the coloring film CF1. Alternatively, impurities can beprevented from being diffused from the light-blocking film BM, thecoloring film CF1, or the like to the layer 753 containing a liquidcrystal material.

Note that a single-layer film or a stacked-layer film can be used forthe insulating film 771. For example, an insulating film 771A and aninsulating film 771B can be used for the insulating film 771.

<<Terminal 519B>>

The display device described in this embodiment includes a terminal 519B(see FIG. 16A).

The terminal 519B includes the conductive layer 511B. The terminal 519Bis electrically connected to the signal line S1(j), for example.

<<Substrate 570 and Substrate 770>>

In addition, the display device described in this embodiment includesthe substrate 570 and the substrate 770.

The substrate 770 includes a region overlapping with the substrate 570.The substrate 770 includes a region positioned such that the functionallayer 520 is sandwiched between the substrate 770 and the substrate 570.

The substrate 770 includes a region overlapping with the first displayelement 750(i,j). For example, a material with low birefringence can beused for the region.

<<Bonding Layer 505, Sealing Material 705, and Structure Body KB1>>

The display device described in this embodiment includes the bondinglayer 505, the sealing material 705, and the structure body KB1.

The bonding layer 505 includes a region positioned between thefunctional layer 520 and the substrate 570, and has a function ofbonding the functional layer 520 and the substrate 570 to each other.

The sealing material 705 includes a region positioned between thefunctional layer 520 and the substrate 770, and has a function ofbonding the functional layer 520 and the substrate 770 to each other.

The structure body KB1 has a function of providing a certain spacebetween the functional layer 520 and the substrate 770.

<<Functional Films 770PA, 770PB, and 770D>>

The display device described in this embodiment includes a functionalfilm 770PA, a functional film 770PB, and the functional film 770D.

The functional films 770PA and 770PB each include a region overlappingwith the first display element 750(i,j).

The functional film 770D includes a region overlapping with the firstdisplay element 750(i,j). The functional film 770D is provided such thatthe substrate 770 lies between the functional film 770D and the firstdisplay element 750(i,j). Thus, for example, light reflected by thefirst display element 750(i,j) can be diffused.

<Example of Components>

The display device 700 includes the substrate 570, the substrate 770,the structure body KB1, the sealing material 705, and the bonding layer505.

The display device 700 also includes the functional layer 520, theoptical element 560, the covering film 565, the insulating film 521, andthe insulating film 528.

The display device 700 also includes the signal line S1(j), the signalline S2(j), the scan line G1(i), the scan line G2(i), the wiring CSCOM,and the wiring ANO.

The display device 700 also includes the first conductive layer and thesecond conductive layer.

The display device 700 also includes the terminal 519B and theconductive layer 511B.

The display device 700 also includes the pixel circuit 530(i,j) and theswitch SW1.

The display device 700 also includes the first display element 750(i,j),the first electrode 751(i,j), the reflective film, the opening, thelayer 753 containing a liquid crystal material, and the second electrode752.

The display device 700 also includes an alignment film AF1, an alignmentfilm AF2, the coloring film CF1, the light-blocking film BM, theinsulating film 771, the functional film 770P, and the functional film770D.

The display device 700 also includes the second display element550(i,j), the electrode 551(i,j), the electrode 552, and the layer553(j) containing a light-emitting material.

The display device 700 also includes the insulating film 501B and theinsulating film 501C.

The display device 700 also includes the driver circuit GD and thedriver circuit SD.

<<Substrate 570>>

The substrate 570 or the like can be formed using a material having heatresistance high enough to withstand heat treatment in the manufacturingprocess. For example, a material with a thickness greater than or equalto 0.1 mm and less than or equal to 0.7 mm can be used for the substrate570. Specifically, a material polished to a thickness of approximately0.1 mm can be used.

For example, a large-sized glass substrate having any of the followingsizes can be used as the substrate 570 or the like: the 6th generation(1500 mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8thgeneration (2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm), andthe 10th generation (2950 mm×3400 mm). Thus, a large-sized displaydevice can be manufactured.

For the substrate 570 or the like, an organic material, an inorganicmaterial, a composite material of an organic material and an inorganicmaterial, or the like can be used. For example, an inorganic materialsuch as glass, ceramic, or a metal can be used for the substrate 570 orthe like.

Specifically, non-alkali glass, soda-lime glass, potash glass, crystalglass, aluminosilicate glass, tempered glass, chemically tempered glass,quartz, sapphire, or the like can be used for the substrate 570 or thelike. Specifically, an inorganic oxide film, an inorganic nitride film,an inorganic oxynitride film, or the like can be used for the substrate570 or the like. For example, a silicon oxide film, a silicon nitridefilm, a silicon oxynitride film, an aluminum oxide film, or the like canbe used for the substrate 570 or the like. Stainless steel, aluminum, orthe like can be used for the substrate 570 or the like.

For example, a single crystal semiconductor substrate or apolycrystalline semiconductor substrate of silicon or silicon carbide, acompound semiconductor substrate of silicon germanium or the like, or anSOI substrate can be used as the substrate 570 or the like. Thus, asemiconductor element can be provided over the substrate 570 or thelike.

For example, an organic material such as a resin, a resin film, orplastic can be used for the substrate 570 or the like. Specifically, aresin film or resin plate of polyester, polyolefin, polyamide,polyimide, polycarbonate, an acrylic resin, or the like can be used forthe substrate 570 or the like.

For example, a composite material formed by attaching a metal plate, athin glass plate, or a film of an inorganic material to a resin film orthe like can be used for the substrate 570 or the like. For example, acomposite material formed by dispersing a fibrous or particulate metal,glass, inorganic material, or the like into a resin film can be used forthe substrate 570 or the like. For example, a composite material formedby dispersing a fibrous or particulate resin, organic material, or thelike into an inorganic material can be used for the substrate 570 or thelike.

Furthermore, a single-layer material or a layered material in which aplurality of layers are stacked can be used for the substrate 570 or thelike. For example, a layered material in which a base, an insulatingfilm that prevents diffusion of impurities contained in the base, andthe like are stacked can be used for the substrate 570 or the like.Specifically, a layered material in which glass and one or more of asilicon oxide layer, a silicon nitride layer, a silicon oxynitridelayer, and the like that prevent diffusion of impurities contained inthe glass are stacked can be used for the substrate 570 or the like.Alternatively, a layered material in which a resin and a film forpreventing diffusion of impurities that penetrate the resin, such as asilicon oxide film, a silicon nitride film, and a silicon oxynitridefilm are stacked can be used for the substrate 570 or the like.

Specifically, a resin film, a resin plate, a layered material, or thelike containing polyester, polyolefin, polyamide, polyimide,polycarbonate, an acrylic resin, or the like can be used for thesubstrate 570 or the like.

Specifically, a material containing polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, polyurethane, anacrylic resin, an epoxy resin, or a resin having a siloxane bond, suchas silicone can be used for the substrate 570 or the like.

Specifically, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), acrylic, or the like can be used for thesubstrate 570 or the like. Alternatively, a cycloolefin polymer (COP), acycloolefin copolymer (COC), or the like can be used.

Alternatively, paper, wood, or the like can be used for the substrate570 or the like.

For example, a flexible substrate can be used as the substrate 570 orthe like.

Note that a transistor, a capacitor, or the like can be directly formedon the substrate. Alternatively, a transistor, a capacitor, or the likeformed on a substrate for use in manufacturing processes that can resistheat applied in the manufacturing process can be transferred to thesubstrate 570 or the like. Thus, a transistor, a capacitor, or the likecan be formed over a flexible substrate, for example.

<<Substrate 770>>

For example, a material that can be used for the substrate 570 can beused for the substrate 770. For example, a light-transmitting materialthat can be used for the substrate 570 can be used for the substrate770. Alternatively, a material having a surface provided with anantireflective film with a thickness of 1 μm or less can be used for thesubstrate 770. Specifically, a stack including three or more, preferablyfive or more, more preferably 15 or more dielectrics can be used for thesubstrate 770. This allows reflectivity to be as low as 0.5% or less,preferably 0.08% or less. Alternatively, a material with lowbirefringence that can be used for the substrate 570 can be used for thesubstrate 770.

For example, aluminosilicate glass, tempered glass, chemically temperedglass, sapphire, or the like can be favorably used for the substrate 770that is on the side closer to a user of the display device. This canprevent breakage or damage of the display device caused by the use.

For example, a resin film of a cycloolefin polymer (COP), a cycloolefincopolymer (COC), or triacetyl cellulose (TAC) can be favorably used asthe substrate 770, in which case the substrate 770 can be lightweight.Alternatively, for example, the display device can be made less likelyto suffer from damage by dropping.

A material with a thickness greater than or equal to 0.1 mm and lessthan or equal to 0.7 mm can be used for the substrate 770, for example.Specifically, a substrate polished to be reduced in the thickness can beused. In that case, the functional film 770D can be close to the firstdisplay element 750(i,j). As a result, image blur can be reduced, and animage can be displayed clearly.

<<Structure Body KB1>>

The structure body KB1 or the like can be formed using an organicmaterial, an inorganic material, or a composite material of an organicmaterial and an inorganic material, for example. Accordingly, apredetermined space can be provided between components between which thestructure body KB1 and the like are provided.

Specifically, for the structure body KB1, polyester, polyolefin,polyamide, polyimide, polycarbonate, polysiloxane, an acrylic resin, orthe like, or a composite material of a plurality of resins selected fromthese can be used. Alternatively, a photosensitive material may be used.

<<Sealing Material 705>>

For the sealing material 705 or the like, an inorganic material, anorganic material, a composite material of an inorganic material and anorganic material, or the like can be used.

For example, an organic material such as a thermally fusible resin or acurable resin can be used for the sealing material 705 or the like.

For example, an organic material such as a reactive curable adhesive, alight curable adhesive, a thermosetting adhesive, and/or an anaerobicadhesive can be used for the sealing material 705 or the like.

Specifically, an adhesive containing an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, or anethylene vinyl acetate (EVA) resin, or the like can be used for thesealing material 705 or the like.

<<Bonding Layer 505>>

For example, any of the materials that can be used for the sealingmaterial 705 can be used for the bonding layer 505.

<<Insulating Film 521>>

For example, an insulating inorganic material, an insulating organicmaterial, an insulating composite material containing an inorganicmaterial and an organic material can be used for the insulating film 521or the like.

Specifically, for example, an inorganic oxide film, an inorganic nitridefilm, an inorganic oxynitride film, or a material obtained by stackingany of these films can be used as the insulating film 521 or the like.For example, a film including any of a silicon oxide film, a siliconnitride film, a silicon oxynitride film, and an aluminum oxide film, ora film including a layered material obtained by stacking any of thesefilms can be used as the insulating film 521 or the like.

Specifically, for the insulating film 521 or the like, polyester,polyolefin, polyamide, polyimide, polycarbonate, polysiloxane, anacrylic resin, or the like, or a laminated or composite material of aplurality of kinds of resins selected from these can be used.Alternatively, a photosensitive material may be used.

Thus, steps due to various components overlapping with the insulatingfilm 521 can be reduced, for example.

<<Optical Element 560>>

The optical element 560 has an optical axis Z (see FIG. 10C). Theoptical axis Z passes through the center of the region of the firstregion 560A to which visible light is supplied and the center of thethird region 560C. The second region 560B includes an inclined portionwith an inclination B of 45° or more, preferably 75° or more and 85° orless, with respect to a plane orthogonal to the optical axis Z. Forexample, the second region 560B illustrated in the drawing entirely hasan inclination of approximately 60° with respect to the plane orthogonalto the optical axis Z.

The inclined portion of the second region 560B is provided withingreater than or equal to 0.05 μm and less than or equal to 0.2 μm of theend of the region of the first region 560A to which visible light issupplied. Note that in the case where the second display element550(i,j) is in contact with the first region 560A, the region of thefirst region 560A to which visible light is supplied has the same areaas the region of the second display element 550(i,j) that can supplyvisible light. For example, the inclined portion of the second region560B illustrated in the drawing is positioned at a distance d from theend of the region of the first region 560A to which visible light issupplied.

The region of the first region 560A to which visible light is suppliedhas an area larger than 10% of the area of the pixel 702(i,j) (see FIG.10D).

The third region 560C has an area smaller than or equal to 10% of thearea of the pixel 702(i,j).

The reflective film 751B has an area larger than or equal to 70% of thearea of the pixel 702(i,j).

The sum of the area of the region of the first region 560A to whichvisible light is supplied and the area of the reflective film 751B islarger than the area of the pixel 702(i,j).

For example, a rectangular pixel 27 μm wide and 81 μm long has an areaof 2187 μm². In the case of such a pixel, the region of the first region560A to which visible light is supplied has an area of 324 μm². Thethird region 560C has an area of 81 μm², and the reflective film 751Bhas an area of 1894 μm².

In this structure, the area of a region of the first region 560A towhich visible light is supplied is approximately 14.8% of the area ofthe pixel.

The area of the reflective film 751B is approximately 86.6% of the areaof the pixel.

The sum of the area of the region of the first region 560A to whichvisible light is supplied and the area of the reflective film 751B is2218 μm².

Thus, in the second region, light incident through the first region atvarious angles can be gathered. Consequently, a novel display devicewith high convenience or high reliability can be provided.

Note that a plurality of materials can be used for the optical element560. For example, a plurality of materials selected such that adifference between their refractive indices is 0.2 or less can be usedfor the optical element 560. Thus, reflection or scattering of light inthe optical element or loss of light can be inhibited.

The optical element 560 can have any of various shapes. For example, theshape of a section orthogonal to the optical axis of the optical element560 can be a circle or a polygon. The second region 560B of the opticalelement 560 can have a flat surface or a curved surface.

An example of a cross-sectional view along the optical axis of theoptical element 560 having a quadrangle section orthogonal to theoptical axis is illustrated in FIG. 23A-1, FIG. 23B-1, or FIG. 23C-1.FIG. 23A-2, FIG. 23B-2, or FIG. 23C-2 shows a perspective view of theoptical element 560.

An example of a cross-sectional view along the optical axis of theoptical element 560 having a circular section orthogonal to the opticalaxis is illustrated in FIG. 23D-1, FIG. 23E-1, or FIG. 23F-1. FIG.23D-2, FIG. 23E-2, or FIG. 23F-2 shows a perspective view of the opticalelement 560.

<<Covering Film 565>>

A single-layer film or a laminated film can be used as the covering film565. For example, a stack including a light-transmitting film and areflective film can be used for the covering film 565.

For example, an inorganic material such as an oxide film, a fluoridefilm, or a sulfide film can be used for the light-transmitting film.

For example, a metal can be used for the reflective film. Specifically,a material containing silver can be used for the covering film 565. Forexample, a material containing silver, palladium, and the like or amaterial containing silver, copper, and the like can be used for thereflective film. Alternatively, a multilayer film of dielectrics can beused for the reflective film.

<<Insulating Film 528>>

For example, any of the materials that can be used for the insulatingfilm 521 can be used for the insulating film 528 or the like.Specifically, a 1-μm-thick polyimide-containing film can be used as theinsulating film 528.

<<Insulating Film 501B>>

For example, a material that can be used for the insulating film 521 canbe used for the insulating film 501B. For example, a material having afunction of supplying hydrogen can be used for the insulating film 501B.

Specifically, a material obtained by stacking a material containingsilicon and oxygen and a material containing silicon and nitrogen can beused for the insulating film 501B. For example, a material having afunction of releasing hydrogen by heating or the like to supply thehydrogen to another component can be used for the insulating film 501B.Specifically, a material having a function of releasing hydrogen takenin the manufacturing process, by heating or the like, to supply thehydrogen to another component can be used for the insulating film 501B.

For example, a film containing silicon and oxygen that is formed by achemical vapor deposition method using silane or the like as a sourcegas can be used as the insulating film 501B.

Specifically, a material obtained by stacking a material containingsilicon and oxygen and having a thickness greater than or equal to 200nm and less than or equal to 600 nm and a material containing siliconand nitrogen and having a thickness of approximately 200 nm can be usedfor the insulating film 501B.

<<Insulating Film 501C>>

For example, any of the materials that can be used for the insulatingfilm 521 can be used for the insulating film 501C. Specifically, amaterial containing silicon and oxygen can be used for the insulatingfilm 501C. Thus, diffusion of impurities into the pixel circuit, thesecond display element, or the like can be inhibited.

For example, a 200-nm-thick film containing silicon, oxygen, andnitrogen can be used as the insulating film 501C.

<<Wiring, Terminal, and Conductive Layer>>

A conductive material can be used for the wiring or the like.Specifically, the conductive material can be used for the signal lineS1(j), the signal line S2(j), the scan line G1(i), the scan line G2(i),the wiring CSCOM, the wiring ANO, the terminal 519B, the conductivelayer 511B, or the like.

For example, an inorganic conductive material, an organic conductivematerial, a metal, conductive ceramics, or the like can be used for thewiring or the like.

Specifically, a metal element selected from aluminum, gold, platinum,silver, copper, chromium, tantalum, titanium, molybdenum, tungsten,nickel, iron, cobalt, palladium, and manganese can be used for thewiring or the like. Alternatively, an alloy containing any of theabove-described metal elements, or the like can be used for the wiringor the like. In particular, an alloy of copper and manganese is suitablyused in microfabrication using a wet etching method.

Specifically, any of the following structures can be used for the wiringor the like: a two-layer structure in which a titanium film is stackedover an aluminum film, a two-layer structure in which a titanium film isstacked over a titanium nitride film, a two-layer structure in which atungsten film is stacked over a titanium nitride film, a two-layerstructure in which a tungsten film is stacked over a tantalum nitridefilm or a tungsten nitride film, a three-layer structure in which atitanium film, an aluminum film, and a titanium film are stacked in thisorder, and the like.

Specifically, a conductive oxide, such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded, can be used for the wiring or the like.

Specifically, a film containing graphene or graphite can be used for thewiring or the like.

For example, a film containing graphene oxide is formed and subjected toreduction, whereby a film containing graphene can be formed. As areducing method, a method with application of heat, a method using areducing agent, or the like can be employed.

A film containing a metal nanowire can be used for the wiring or thelike, for example. Specifically, a nanowire containing silver can beused.

Specifically, a conducting polymer can be used for the wiring or thelike.

Note that the terminal 519B can be electrically connected to a flexibleprinted circuit FPC1 with the use of a conductive material ACF1, forexample.

<<First Conductive Layer and Second Conductive Layer>>

For example, any of the materials that can be used for the wiring or thelike can be used for the first conductive layer or the second conductivelayer.

The first electrode 751(i,j), the wiring, or the like can be used forthe first conductive layer.

The conductive layer 512B functioning as the source electrode or thedrain electrode of the transistor that can be used for the switch SW1,the wiring, or the like can be used for the second conductive layer.

<<First Display Element 750(i,j)>>

For example, a display element having a function of controllingtransmission or reflection of light can be used as the first displayelement 750(i,j). For example, a combined structure of a liquid crystalelement and a polarizing plate, a MEMS shutter display element, a MEMSoptical coherence display element, or the like can be used. The use of areflective display element can reduce the power consumption of thedisplay device. For example, a display element using a microcapsulemethod, an electrophoretic method, an electrowetting method, or the likecan be used as the first display element 750(i,j). Specifically, areflective liquid crystal display element can be used as the firstdisplay element 750(i,j).

For example, a liquid crystal element driven in any of the followingdriving modes can be used: an in-plane switching (IPS) mode, a twistednematic (TN) mode, a fringe field switching (FFS) mode, an axiallysymmetric aligned micro-cell (ASM) mode, an optically compensatedbirefringence (OCB) mode, a ferroelectric liquid crystal (FLC) mode, anantiferroelectric liquid crystal (AFLC) mode, and the like.

Alternatively, a liquid crystal element that can be driven by, forexample, a vertical alignment (VA) mode such as a multi-domain verticalalignment (MVA) mode, a patterned vertical alignment (PVA) mode, anelectrically controlled birefringence (ECB) mode, a continuous pinwheelalignment (CPA) mode, or an advanced super view (ASV) mode can be used.

The first display element 750(i,j) includes a first electrode, a secondelectrode, and a layer containing a liquid crystal material. The layercontaining a liquid crystal material contains a liquid crystal materialwhose alignment can be controlled by voltage applied between the firstelectrode and the second electrode. For example, the alignment of theliquid crystal material can be controlled by an electric field in thethickness direction (also referred to as the vertical direction) or anelectric field in the direction that intersects the vertical direction(also referred to as the horizontal direction or the diagonal direction)of the layer containing a liquid crystal material.

<<Layer 753 Containing Liquid Crystal Material>>

For example, thermotropic liquid crystal, low-molecular liquid crystal,high-molecular liquid crystal, polymer dispersed liquid crystal,ferroelectric liquid crystal, anti-ferroelectric liquid crystal, or thelike can be used for the layer containing a liquid crystal material.Alternatively, a liquid crystal material which exhibits a cholestericphase, a smectic phase, a cubic phase, a chiral nematic phase, anisotropic phase, or the like can be used. Alternatively, a liquidcrystal material which exhibits a blue phase can be used.

For example, a negative liquid crystal material can be used for thelayer containing a liquid crystal material.

For example, a liquid crystal material having a resistivity of greaterthan or equal to 1.0×10¹³ Ω·cm, preferably greater than or equal to1.0×10¹⁴ Ω·cm, more preferably greater than or equal to 1.0×10¹⁵ Ω·cm,is used for the layer 753 containing a liquid crystal material. This cansuppress a variation in the transmittance of the first display element750(i,j). Alternatively, flickering of the first display element750(i,j) can be suppressed. Alternatively, the rewriting frequency ofthe first display element 750(i,j) can be reduced.

<<First Electrode 751(i,j)>>

For example, the material that is used for the wiring or the like can beused for the first electrode 751(i,j). Specifically, a reflective filmcan be used for the first electrode 751(i,j). For example, a material inwhich a light-transmitting conductive layer and a reflective film havingan opening are stacked can be used for the first electrode 751(i,j).

<<Reflective Film>>

For example, a material that reflects visible light can be used for thereflective film. Specifically, a material containing silver can be usedfor the reflective film. For example, a material containing silver,palladium, and the like or a material containing silver, copper, and thelike can be used for the reflective film.

The reflective film reflects light that passes through the layer 753containing a liquid crystal material, for example. This allows the firstdisplay element 750 to serve as a reflective liquid crystal element.Alternatively, for example, a material with unevenness on its surfacecan be used for the reflective film. In that case, incident light can bereflected in various directions so that a white image can be displayed.

For example, the first conductive layer, the first electrode 751(i,j),or the like can be used as the reflective film.

For example, a film including a region positioned such that alight-transmitting conductive layer 751A is sandwiched between theregion and the layer 753 containing a liquid crystal material can beused as the reflective film 751B (see FIG. 20A).

For example, a film including a region positioned between the layer 753containing a liquid crystal material and a light-transmitting conductivelayer 751C can be used as the reflective film 751B (see FIG. 20B).

For example, a film including a region positioned between thelight-transmitting conductive layer 751A and the light-transmittingconductive layer 751C can be used as the reflective film 751B (see FIG.20C).

For example, a film reflecting visible light may be used for the firstelectrode 751(i,j) (see FIG. 20D).

The reflective film has a shape including the region 751H where lightemitted from the second display element 550(i,j) is not blocked (seeFIGS. 21A to 21C).

For example, the reflective film can have one or more openings.Specifically, the region 751H may have a polygonal shape, a quadrangularshape, an elliptical shape, a circular shape, a cross-like shape, or thelike. The region 751H may alternatively have a stripe shape, a slit-likeshape, or a checkered pattern.

If the ratio of the total area of the region 751H to the total area ofthe reflective film is too large, an image displayed using the firstdisplay element 750(i,j) is dark.

If the ratio of the total area of the region 751H to the total area ofthe reflective film is too small, an image displayed using the seconddisplay element 550(i,j) is dark. The reliability of the second displayelement 550(i,j) may be degraded.

For example, the region 751H provided in the pixel 702(i,j+1) is notprovided on a line that extends in the row direction (the directionindicated by the arrow R1 in the drawing) through the region 751Hprovided in the pixel 702(i,j) (see FIG. 21A). Alternatively, forexample, the region 751H provided in the pixel 702(i+1,j) is notprovided on a line that extends in the column direction (the directionindicated by the arrow C1 in the drawing) through the region 751Hprovided in the pixel 702(i,j) (see FIG. 21B).

For example, the region 751H provided in the pixel 702(i,j+2) isprovided on a line that extends in the row direction through the region751H provided in the pixel 702(i,j) (see FIG. 21A). In addition, theregion 751H provided in the pixel 702(i,j+1) is provided on a line thatis perpendicular to the above line between the region 751H provided inthe pixel 702(i,j) and the region 751H provided in the pixel 702(i,j+2).

Alternatively, for example, the region 751H provided in the pixel702(i,j+2,j) is provided on a line that extends in the column directionthrough the region 751H provided in the pixel 702(i,j) (see FIG. 21B).In addition, for example, the region 751H provided in the pixel702(i+1,j) is provided on a line that is perpendicular to the above linebetween the region 751H provided in the pixel 702(i,j) and the region751H provided in the pixel 702(i,j+2,j).

When the second display elements are provided in the above manner tooverlap with the regions where light is not blocked, the second displayelement of one pixel adjacent to another pixel can be apart from asecond display element of the another pixel. A display element thatdisplays color different from that displayed from the second displayelement of one pixel can be provided as the second display element ofanother pixel adjacent to the one pixel. The difficulty in arranging aplurality of display elements that represent different colors adjacentto each other can be lowered. Thus, a novel display device with highconvenience or high reliability can be provided.

The reflective film can have a shape in which an end portion is cut offso as to form the region 751H (see FIG. 21C). Specifically, thereflective film can have a shape in which an end portion is cut off soas to be shorter in the column direction (the direction indicated by thearrow C1 in the drawing).

<<Second Electrode 752>>

For example, a material that can be used for the wiring or the like canbe used for the second electrode 752. For example, a material that has alight-transmitting property selected from materials that can be used forthe wiring or the like can be used for the second electrode 752.

For example, a conductive oxide, a metal film thin enough to transmitlight, a metal nanowire, or the like can be used for the secondelectrode 752.

Specifically, a conductive oxide containing indium can be used for thesecond electrode 752. Alternatively, a metal thin film with a thicknessgreater than or equal to 1 nm and less than or equal to 10 nm can beused for the second electrode 752. Alternatively, a metal nanowirecontaining silver can be used for the second electrode 752.

Specifically, indium oxide, indium tin oxide, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, zinc oxide to whichaluminum is added, or the like can be used for the second electrode 752.

<<Alignment Films AF1 and AF2>>

The alignment films AF1 and AF2 can be formed using a materialcontaining polyimide or the like, for example. Specifically, a materialformed by rubbing treatment or an optical alignment technique such thata liquid crystal material has predetermined alignment can be used.

For example, a film containing soluble polyimide can be used for thealignment film AF1 or AF2. In that case, the temperature required informing the alignment film AF1 or AF2 can be low. As a result, damage toother components caused when the alignment film AF1 or the alignmentfilm AF2 is formed can be reduced.

<<Coloring Film CF1>>

The coloring film CF1 can be formed using a material transmitting lightof a certain color and can thus be used for a color filter or the like.

For example, a material that transmits blue light, green light, or redlight can be used for the coloring film CF1. In that case, the spectralwidth of light that is transmitted through the coloring film CF1 can benarrowed, so that clear display can be provided.

Furthermore, for example, a material that absorbs blue light, greenlight, or red light can be used for the coloring film CF1. Specifically,a material transmitting yellow light, magenta light, or cyan light canbe used for the coloring film CF1. In that case, the spectral width oflight that is absorbed by the coloring film CF1 can be narrowed, so thatbright display can be provided.

<<Light-Blocking Film BM>>

The light-blocking film BM can be formed with a material that preventslight transmission and can thus be used as a black matrix, for example.

Specifically, a resin containing a pigment or dye can be used for thelight-blocking film BM. For example, a resin in which carbon black isdispersed can be used for the blocking film.

Alternatively, an inorganic compound, an inorganic oxide, a compositeoxide containing a solid solution of a plurality of inorganic oxides, orthe like can be used for the light-blocking film BM. Specifically, ablack chromium film, a film containing cupric oxide, or a filmcontaining copper chloride or tellurium chloride can be used for thelight-blocking film BM.

<<Insulating Film 771>>

For example, a material that can be used for the insulating film 521 canbe used for the insulating film 771. The insulating film 771 can beformed of polyimide, an epoxy resin, an acrylic resin, or the like.Alternatively, a film including any of a silicon oxide film, a siliconnitride film, a silicon oxynitride film, and an aluminum oxide film, andthe like, or a film including a layered material obtained by stackingany of these films can be used for the insulating film 771.

<<Functional Films 770P and 770D>>

An antireflective film, a polarizing film, a retardation film, a lightdiffusion film, a condensing film, or the like can be used for thefunctional film 770P or the functional film 770D, for example.

Specifically, a film containing a dichromatic pigment can be used forthe functional film 770P or the functional film 770D. Alternatively, amaterial with a columnar structure having an axis along the directionintersecting a surface of a base can be used for the functional film770P or the functional film 770D. In that case, light can be easilytransmitted in the direction along the axis and easily scattered inother directions.

Alternatively, an antistatic film preventing the attachment of a foreignsubstance, a water repellent film suppressing the attachment of stain, ahard coat film suppressing a scratch in use, or the like can be used asthe functional film 770P.

Specifically, a circularly polarizing film can be used for thefunctional film 770P. Furthermore, a light diffusion film can be usedfor the functional film 770D.

<<Second Display Element 550(i,j)>>

For example, a display element having a function of emitting light canbe used as the second display element 550(i,j). Specifically, an organicelectroluminescent element, an inorganic electroluminescent element, alight-emitting diode, a quantum-dot LED (QDLED), or the like can be usedas the second display element 550(i,j).

For example, a light-emitting organic compound can be used for the layer553(j) containing a light-emitting material.

For example, quantum dots can be used for the layer 553(j) containing alight-emitting material. Accordingly, the half width becomes narrow, andlight of a bright color can be emitted.

A layered material for emitting blue light, green light, or red lightcan be used for the layer 553(j) containing a light-emitting material,for example.

For example, a belt-like layered material that extends in the columndirection along the signal line S2(j) can be used for the layer 553(j)containing a light-emitting material.

Alternatively, a layered material for emitting white light can be usedfor the layer 553(j) containing a light-emitting material. Specifically,a layered material in which a layer containing a light-emitting materialincluding a fluorescent material that emits blue light, and a layercontaining materials that are other than a fluorescent material and thatemit green light and red light or a layer containing a material that isother than a fluorescent material and that emits yellow light arestacked can be used for the layer 553(j) containing a light-emittingmaterial.

For example, the material that can be used for the wiring or the likecan be used for the electrode 551(i,j).

For example, a material that transmits visible light among the materialsthat can be used for the wiring or the like can be used for theelectrode 551(i,j).

Specifically, conductive oxide, indium-containing conductive oxide,indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zincoxide to which gallium is added, or the like can be used for theelectrode 551(i,j). Alternatively, a metal film that is thin enough totransmit light can be used as the electrode 551(i,j). Furtheralternatively, a metal film that transmits part of light and reflectsanother part of light can be used for the electrode 551(i,j).Accordingly, the second display element 550(i,j) can have a microcavitystructure. As a result, light of a predetermined wavelength can beextracted more efficiently than light of other wavelengths.

For example, a material that can be used for the wiring or the like canbe used for the electrode 552. Specifically, a material that reflectsvisible light can be used for the electrode 552.

<<Driver Circuit GD>>

Any of a variety of sequential circuits, such as a shift register, canbe used as the driver circuit GD. For example, a transistor MD, acapacitor, and the like can be used in the driver circuit GD.Specifically, a transistor including a semiconductor film that can beformed in the same process as the semiconductor film of the transistor Mor the transistor that can be used as the switch SW1 can be used.

As the transistor MD, a transistor having a structure different fromthat of the transistor that can be used as the switch SW1 can be used,for example.

Note that the transistor MD can have the same structure as thetransistor M.

<<Transistor>>

For example, semiconductor films formed in the same process can be usedfor transistors in the driver circuit and the pixel circuit.

As the transistor in the driver circuit or the pixel circuit, abottom-gate transistor or a top-gate transistor can be used, forexample.

A manufacturing line for a bottom-gate transistor including amorphoussilicon as a semiconductor can be easily remodeled into a manufacturingline for a bottom-gate transistor including an oxide semiconductor as asemiconductor, for example. Furthermore, for example, a manufacturingline for a top-gate transistor including polysilicon as a semiconductorcan be easily remodeled into a manufacturing line for a top-gatetransistor including an oxide semiconductor as a semiconductor. Ineither reconstruction, a conventional manufacturing line can beeffectively used.

For example, a transistor including a semiconductor containing anelement belonging to Group 14 for a semiconductor film can be used.Specifically, a semiconductor containing silicon can be used for asemiconductor film. For example, single crystal silicon, polysilicon,microcrystalline silicon, or amorphous silicon can be used for thesemiconductor film of the transistor.

Note that the temperature for forming a transistor using polysilicon asa semiconductor is lower than the temperature for forming a transistorusing single crystal silicon as a semiconductor.

In addition, the transistor using polysilicon as a semiconductor hashigher field-effect mobility than the transistor using amorphous siliconas a semiconductor, and therefore a pixel including the transistor usingpolysilicon can have a high aperture ratio. Moreover, pixels arranged athigh resolution, a gate driver circuit, and a source driver circuit canbe formed over the same substrate. As a result, the number of componentsincluded in an electronic device can be reduced.

In addition, the transistor using polysilicon as a semiconductor hashigher reliability than the transistor using amorphous silicon as asemiconductor.

Alternatively, a transistor including a compound semiconductor can beused. Specifically, a semiconductor containing gallium arsenide can beused for a semiconductor film.

Alternatively, a transistor including an organic semiconductor can beused. Specifically, an organic semiconductor containing any ofpolyacenes and graphene can be used for a semiconductor film.

For example, a transistor using an oxide semiconductor for asemiconductor film can be used. Specifically, an oxide semiconductorcontaining indium or an oxide semiconductor containing indium, gallium,and zinc can be used for a semiconductor film. Note that the details ofthe oxide semiconductor example will be described in Embodiment 4.

For example, a transistor having a lower leakage current in an off statethan a transistor using amorphous silicon for a semiconductor film canbe used. Specifically, a transistor using an oxide semiconductor for asemiconductor film can be used.

Thus, a pixel circuit can hold an image signal for a longer time than apixel circuit including a transistor that uses amorphous silicon for asemiconductor film. Specifically, the selection signal can be suppliedat a frequency of lower than 30 Hz, preferably lower than 1 Hz, morepreferably less than once per minute while flickering is suppressed.Consequently, eyestrain on a user of a data processing device thatincludes the above pixel circuit can be reduced, and power consumptionfor driving can be reduced.

For example, a transistor including a semiconductor film 508, aconductive layer 504, the conductive layer 512A, and the conductivelayer 512B can be used as the switch SW1 (see FIG. 16B). The insulatingfilm 506 includes a region positioned between the semiconductor film 508and the conductive layer 504.

The conductive layer 504 includes a region overlapping with thesemiconductor film 508. The conductive layer 504 functions as a gateelectrode. The insulating film 506 functions as a gate insulating film.

The conductive layers 512A and 512B are electrically connected to thesemiconductor film 508. The conductive layer 512A has one of a functionof a source electrode and a function of a drain electrode, and theconductive layer 512B has the other.

Furthermore, a transistor including the conductive layer 524 can be usedas the transistor included in the driver circuit or the pixel circuit(see FIG. 16B). The conductive layer 524 includes a region provided suchthat the semiconductor film 508 is positioned between the conductivelayer 504 and the conductive layer 524. The insulating film 516 includesa region positioned between the conductive layer 524 and thesemiconductor film 508. For example, the conductive layer 524 can beelectrically connected to a wiring that supplies the same potential asthat supplied to the conductive layer 504.

A conductive layer in which a 10-nm-thick film containing tantalum andnitrogen and a 300-nm-thick film containing copper are stacked can beused as the conductive layer 504, for example. A film containing copperincludes a region provided such that a film containing tantalum andnitrogen is positioned between the film containing copper and theinsulating film 506.

A material in which a 400-nm-thick film containing silicon and nitrogenand a 200-nm-thick film containing silicon, oxygen, and nitrogen arestacked can be used for the insulating film 506, for example. Note thatthe film containing silicon and nitrogen includes a region provided suchthat the film containing silicon, oxygen, and nitrogen is positionedbetween the film containing silicon and nitrogen and the semiconductorfilm 508.

For example, a 25-nm-thick film containing indium, gallium, and zinc canbe used as the semiconductor film 508.

For example, a conductive layer in which a 50-nm-thick film containingtungsten, a 400-nm-thick film containing aluminum, and a 100-nm-thickfilm containing titanium are stacked can be used as the conductive layer512A or 512B. Note that the film containing tungsten includes a regionin contact with the semiconductor film 508.

<Structural Example 6 of Display Device>

A structure of a display device of one embodiment of the presentinvention will be described with reference to FIGS. 12A and 12B.

FIGS. 12A and 12B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 12A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 12B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 12A.

The structure of the display device described in this structural exampleis the same as that of the display device 700 described with referenceto FIGS. 11A and 11B except that a lens 580 is provided. Differentportions will be described in detail below, and the above description isreferred to for the similar portions.

The display device described in this embodiment includes the lens 580.The lens 580 includes a region positioned between the optical element560 and the second display element 550(i,j) (see FIGS. 12A and 12B).

The lens 580 is a convex lens that includes a material with a refractiveindex of 1.5 or more and 2.5 or less.

With such a structure, light emitted from the second display element canbe gathered toward the optical axis of the optical element, for example.Alternatively, light emitted from the second display element can be usedefficiently. The density of current flowing through the light-emittingelement can be decreased. Alternatively, the area of the second displayelement can be increased. Alternatively, the reliability of thelight-emitting element can be increased. For example, an organic ELelement or a light-emitting diode can be used as the light-emittingelement. Consequently, a novel display device with high convenience orhigh reliability can be provided.

For example, a plano-convex lens can be used as the lens 580.

<<Lens 580>>

A plano-convex lens or a double-convex lens can be used as the lens 580.

A material that transmits visible light can be used for the lens 580.Alternatively, a material whose refractive index is greater than orequal to 1.3 and less than or equal to 2.5 can be used for the lens 580.For example, an inorganic material or an organic material can be usedfor the lens 580.

For example, a material including an oxide or a sulfide can be used forthe lens 580.

Specifically, cerium oxide, hafnium oxide, lanthanum oxide, magnesiumoxide, niobium oxide, tantalum oxide, titanium oxide, yttrium oxide,zinc oxide, an oxide containing indium and tin, an oxide containingindium, gallium, and zinc, or the like can be used for the lens 580.Alternatively, zinc sulfide or the like can be used for the lens 580.

For example, the lens 580 can be formed using a material containing aresin. Specifically, the lens 580 can be formed using a resin to whichchlorine, bromine, or iodine is introduced, a resin to which a heavymetal atom is introduced, a resin to which an aromatic ring isintroduced, a resin to which sulfur is introduced, or the like.Alternatively, the lens 580 can be formed using a material containing aresin and nanoparticles of a material whose refractive index is higherthan that of the resin. Titanium oxide, zirconium oxide, or the like canbe used for the nanoparticles.

<Structural Example 7 of Display Device>

A structure of a display device of one embodiment of the presentinvention is described with reference to FIGS. 13A and 13B.

FIGS. 13A and 13B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 13A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 13B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 13A.

The structure of the display device described in this structural exampleis the same as that of the display device 700 described with referenceto FIGS. 11A and 11B except that a liquid crystal element that canoperate in a guest-host liquid crystal mode is used as the first displayelement 750(i,j) and that a bottom-gate transistor is used. Differentportions will be described in detail below, and the above description isreferred to for the similar portions.

The display device described in this embodiment includes a liquidcrystal element that can operate in a guest-host liquid crystal mode asthe first display element 750(i,j). Thus, a reflective display devicecan be obtained without a polarizing plate. Furthermore, an imagedisplayed by the display device can be made bright.

<<Layer 753 Containing Liquid Crystal Material>>

For example, nematic liquid crystal, thermotropic liquid crystal,low-molecular liquid crystal, high-molecular liquid crystal, polymerdispersed liquid crystal, or the like can be used for the layercontaining a liquid crystal material. Alternatively, a liquid crystalmaterial which exhibits a cholesteric phase or the like can be used.Alternatively, a liquid crystal material which exhibits a blue phase canbe used.

Furthermore, the layer 753 containing a liquid crystal material cancontain a dichromatic colorant. Note that a liquid crystal materialcontaining a dichroic dye is called a guest-host liquid crystal.

Specifically, a material that has high absorbance in the major axisdirection of molecules and low absorbance in the minor-axis directionorthogonal to the major axis direction can be used for the dichroic dye.It is preferable to use a material with a dichroic ratio of 10 orhigher, further preferably 20 or higher for the dichroic dye.

An azo dye, an anthraquinone dye, a dioxazine dye, or the like can beused as the dichroic dye, for example.

Two liquid crystal layers including dichroic dyes having homogeneousalignment that are stacked such that their alignment directions areorthogonal to each other can be used as the layer containing a liquidcrystal material. With the structure, light can be easily absorbed inall directions. Contrast can be increased.

A phase transition guest-host liquid crystal or a structure in which adroplet containing a guest-host liquid crystal is dispersed in a polymercan be used for the layer 753 containing a liquid crystal material.

<Structural Example 8 of Display Device>

A structure of a display device of one embodiment of the presentinvention is described with reference to FIGS. 14A and 14B.

FIGS. 14A and 14B illustrate the structure of the display device of oneembodiment of the present invention. FIG. 14A is a cross-sectional viewof the pixel, which corresponds to the cross-sectional view taken alongline Y1-Y2 in FIG. 10A. FIG. 14B is a cross-sectional view illustratingpart of the structure of the pixel in FIG. 14A.

The structure of the display device described in this structural exampleis the same as that of the display device 700 described with referenceto FIGS. 13A and 13B except that the lens 580 is provided.

<Operation Example of Display Device>

Operation of the display device of one embodiment of the presentinvention is described with reference to FIGS. 24A to 24C.

FIGS. 24A to 24C each illustrate operation of the display device of oneembodiment of the present invention. FIG. 24A is a cross-sectional viewillustrating an operation state of part of the pixel illustrated in FIG.11A, and FIG. 24B is a cross-sectional view illustrating an operationstate different from that in FIG. 24A. FIG. 24C is a cross-sectionalview illustrating an operation state different from that in FIG. 24A orFIG. 24B. Note that dashed arrows shown in the drawings denote thedirections in which external light is incident on and reflected by thefirst display element 750(i,j). A solid arrow in the drawing denotes thedirection in which the second display element 550(i,j) emits light.

<<Operation State 1>>

FIG. 24A illustrates an operation state in which a liquid crystalmaterial LC is aligned in the thickness direction of the layer 753containing a liquid crystal material. For example, the alignment of theliquid crystal material LC is controlled with an alignment film.

When a circularly polarizing plate, the reflective film 751B, and aVA-IPS mode are used, for example, a low gray level can be displayed inthis operation state with no electric field applied. In other words,operation of a normally black liquid crystal display element isachieved.

Although not illustrated, in the case of using the reflective film 751Band a guest-host liquid crystal mode, for example, a high gray level canbe displayed in this operation state with no electric field applied. Inother words, operation of a normally white liquid crystal displayelement is achieved.

<<Operation State 2>>

In the operation state illustrated in FIG. 24B, the second displayelement 550 emits light while the liquid crystal material LC is alignedin the thickness direction of the layer 753 containing a liquid crystalmaterial. Note that the light emitted by the second display element550(i,j) does not pass through the layer 753 containing a liquid crystalmaterial but passes through the structure body KB1.

In the case of using a circularly polarizing plate, the reflective film751B, and a VA-IPS mode, for example, display can be performed with thesecond display element 550 while a low gray level is displayed by thefirst display element 750(i,j) in this operation state with no electricfield applied. In this manner, an image can be displayed with a highcontrast. Alternatively, an image can be displayed with bright colors.

<<Operation State 3>>

FIG. 24C illustrates an operation state in which the liquid crystalmaterial LC is aligned in the direction intersecting the thicknessdirection of the layer 753 containing a liquid crystal material. Forexample, the alignment of the liquid crystal material LC is controlledwith an electric field.

When a circularly polarizing plate, the reflective film 751B, and aVA-IPS mode are used, for example, a high gray level can be displayed.

Although not illustrated, in the case of using the reflective film 751Band a guest-host liquid crystal mode, for example, a low gray level canbe displayed without a polarizing plate.

When the electrode with a comb-like shape illustrated in FIGS. 22A and22B and FIGS. 24A to 24C is provided, the touch sensor described inEmbodiment 1 can be easily incorporated in the first display element.

Note that a hybrid display method is a method for displaying a pluralityof lights in one pixel or one subpixel to display a letter and/or animage. A hybrid display is an aggregate which displays a plurality oflights in one pixel or one subpixel included in a display portion todisplay a letter and/or an image.

As an example of the hybrid display method, a method in which firstlight and second light are displayed with different timings in one pixelor one subpixel can be given. At this time, in one pixel or onesubpixel, the first light and the second light having the same colortone (any one of red, green, and blue, or any one of cyan, magenta, andyellow) can be displayed at the same time, and a letter and/or an imagecan be displayed on a display portion.

As another example of the hybrid display method, a method in whichreflected light and self-emission light are displayed in one pixel orone subpixel can be given. Reflected light and self-emission light(e.g., organic electroluminescent light and light emitted from alight-emitting diode (LED)) having the same color tone can be displayedat the same time in one pixel or one subpixel.

Note that in a hybrid display method, a plurality of lights may bedisplayed in not one pixel or one subpixel but adjacent pixels oradjacent subpixels. Furthermore, displaying first light and second lightat the same time means displaying the first light and the second lightfor the same length of time to the extent that flickering is notperceived by a viewer's eye. As long as flickering is not perceived by aviewer's eye, the display period of the first light may deviate from thedisplay period of the second light.

Moreover, the hybrid display is an aggregate which includes a pluralityof display elements in one pixel or one subpixel and in which theplurality of display elements perform display in the same period. Thehybrid display includes the plurality of display elements and activeelements for driving the display elements in one pixel or one subpixel.As the active elements, switches, transistors, thin film transistors, orthe like can be given. The active element is connected to each of theplurality of display elements, so that display of the plurality ofdisplay elements can be individually controlled.

In Embodiment 2, one embodiment of the present invention has beendescribed. Other embodiments of the present invention will be describedin Embodiments 1, 3, and 4. Note that one embodiment of the presentinvention is not limited to these embodiments. In other words, variousembodiments of the invention are described in in this embodiment and theother embodiments, and one embodiment of the present invention is notlimited to a particular embodiment. Although an example in which oneembodiment of the present invention is applied to a display device isdescribed, one embodiment of the present invention is not limitedthereto. Depending on circumstances or conditions, one embodiment of thepresent invention is not necessarily applied to a display device. Oneembodiment of the present invention may be applied to a semiconductordevice with another function, for example. Although an example in whicha channel formation region, a source region, a drain region, and thelike of a transistor contain an oxide semiconductor is described as oneembodiment of the present invention, one embodiment of the presentinvention is not limited thereto. Depending on circumstances orconditions, various transistors or a channel formation region, a sourceregion, a drain region, and the like of a transistor in one embodimentof the present invention may contain a variety of semiconductors.Depending on circumstances or conditions, various transistors or achannel formation region, a source region, a drain region, and the likeof a transistor in one embodiment of the present invention may containat least one of silicon, germanium, silicon germanium, silicon carbide,gallium arsenide, aluminum gallium arsenide, indium phosphide, galliumnitride, and an organic semiconductor, for example, or alternatively donot necessarily contain an oxide semiconductor.

The structure and method described in this embodiment can be implementedby being combined as appropriate with any of the other structures andmethods described in the other embodiments.

Embodiment 3

In this embodiment, the structures of a data processing device of oneembodiment of the present invention will be described with reference toFIGS. 25A to 25E and FIGS. 26A to 26E.

FIGS. 25A to 25E and FIGS. 26A to 26E illustrate the structures of thedata processing device of one embodiment of the present invention. FIG.25A is a block diagram of the data processing device, and FIGS. 25B to25E are perspective views illustrating the structures of the dataprocessing device. FIGS. 26A to 26E are perspective views illustratingthe structures of the data processing device.

<Data Processing Device>

A data processing device 5200B described in this embodiment includes anarithmetic device 5210 and an input/output device 5220 (see FIG. 25A).

The arithmetic device 5210 has a function of receiving operation dataand a function of supplying image data on the basis of the operationdata.

The input/output device 5220 includes a display portion 5230, an inputportion 5240, a sensor portion 5250, and a communication portion 5290and has a function of supplying operation data and a function ofreceiving image data. The input/output device 5220 also has a functionof supplying sensing data, a function of supplying communication data,and a function of receiving communication data.

The input portion 5240 has a function of supplying operation data. Forexample, the input portion 5240 supplies operation data on the basis ofoperation by the user of the data processing device 5200B.

Specifically, a keyboard, a hardware button, a pointing device, a touchsensor, an audio input device, a viewpoint input device, or the like canbe used as the input portion 5240.

The display portion 5230 includes a display device and has a function ofdisplaying image data. For example, the display device described inEmbodiment 1 can be used for the display portion 5230.

The sensor portion 5250 has a function of supplying sensing data. Forexample, the sensor portion 5250 has a function of sensing a surroundingenvironment where the data processing device is used and supplyingsensing data.

Specifically, an illuminance sensor, an imaging device, an attitudedetermination device, a pressure sensor, a human motion sensor, or thelike can be used as the sensor portion 5250.

The communication portion 5290 has a function of receiving and supplyingcommunication data. For example, the communication portion 5290 has afunction of being connected to another electronic device or acommunication network by wireless communication or wired communication.Specifically, the communication portion 5290 has a function of localarea wireless communication, telephone communication, or near fieldwireless communication, for example.

<<Structural Example 1 of Data Processing Device>>

For example, the display portion 5230 can have an outer shape along acylindrical column (see FIG. 25B). Furthermore, the display portion 5230has a function of changing a displaying method in accordance with theilluminance of a usage environment and a function of changing displayedcontents when sensing the existence of a person. Thus, the dataprocessing device can be mounted on a column of a building, for example.Alternatively, the data processing device can display advertisement,information, or the like. The data processing device can be used for adigital signage or the like.

<<Structural Example 2 of Data Processing Device>>

For example, the data processing device has a function of generatingimage data on the basis of the path of a pointer used by a user (seeFIG. 25C). Specifically, it is possible to use a display device with adiagonal of 20 inches or more, preferably 40 inches or more, furtherpreferably 55 inches or more. Alternatively, display devices can bearranged in one display region. Alternatively, display devices can bearranged to be used as a multiscreen. In this case, the data processingdevice can be used for an electronic blackboard, an electronic bulletinboard, a digital signage, or the like.

<<Structural Example 3 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 25D). Thus, it is possible to obtain a smartwatchwith reduced power consumption, for example. Alternatively, it ispossible to obtain a smartwatch that can display an image such that thesmartwatch is favorably used even in an environment with intenseexternal light, e.g., in the open air under fine weather.

<<Structural Example 4 of Data Processing Device>>

The display portion 5230 has a surface gently curved along a sidesurface of a housing (see FIG. 25E). The display portion 5230 includes adisplay device that has, for example, a function of performing displayon a front surface, side surfaces, and a top surface. Thus, it ispossible to obtain a mobile phone that can display image data on notonly its front surface but also its side surfaces and top surface.

<<Structural Example 5 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 26A). Thus, it is possible to obtain a smartphonewith reduced power consumption. Alternatively, it is possible to obtaina smartphone that can display an image such that the smartphone isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

<<Structural Example 6 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 26B). Thus, it is possible to obtain a televisionsystem that can display an image such that the television system isfavorably used even when exposed to intense external light poured into aroom in a sunny day.

<<Structural Example 7 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 26C). Thus, it is possible to obtain a tabletcomputer that can display an image such that the tablet computer isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

<<Structural Example 8 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 26D). Thus, it is possible to obtain a digitalcamera that can display a subject such that an image is favorably viewedeven in an environment with intense external light, e.g., in the openair under fine weather.

<<Structural Example 9 of Data Processing Device>>

For example, the data processing device has a function of changing adisplaying method in accordance with the illuminance of a usageenvironment (see FIG. 26E). Thus, it is possible to obtain a personalcomputer that can display an image such that the personal computer isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

Embodiment 4

[Transistor]

The transistor includes a conductive layer serving as a gate electrode,a semiconductor layer, a conductive layer serving as a source electrode,a conductive layer serving as a drain electrode, and an insulating layerserving as a gate insulating layer. FIGS. 13A and 13B show the casewhere a bottom-gate transistor is used.

Note that there is no particular limitation on the structure of thetransistor included in the display device of one embodiment of thepresent invention. For example, a planar transistor, a staggeredtransistor, or an inverted staggered transistor may be used. A top-gatetransistor or a bottom-gate transistor may be used. Gate electrodes maybe provided above and below a channel.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

As a semiconductor material used for the transistors, a metal oxidewhose energy gap is greater than or equal to 2 eV, preferably greaterthan or equal to 2.5 eV, further preferably greater than or equal to 3eV can be used. A typical example thereof is a metal oxide containingindium, and for example, a CAC-OS described later or the like can beused.

A transistor with a metal oxide having a larger band gap and a lowercarrier density than silicon has a low off-state current; therefore,charges stored in a capacitor that is series-connected to the transistorcan be held for a long time.

The semiconductor layer can be, for example, a film represented by anIn-M-Zn-based oxide that contains indium, zinc, and M (a metal such asaluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum,cerium, tin, neodymium, or hafnium).

In the case where the metal oxide contained in the semiconductor layercontains an In-M-Zn-based oxide, it is preferable that the atomic ratioof metal elements of a sputtering target used for forming a film of theIn-M-Zn oxide satisfy In≥M and Zn≥M The atomic ratio of metal elementsin such a sputtering target is preferably, for example, In:M:Zn=1:1:1,In:M:Zn=1:1:1.2, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1,In:M:Zn=5:1:6, In:M:Zn=5:1:7, or In:M:Zn=5:1:8. Note that the atomicratio of metal elements in the formed semiconductor layer varies fromthe above atomic ratios of metal elements of the sputtering targets in arange of ±40%.

The bottom-gate transistor described in this embodiment is preferablebecause the number of manufacturing steps can be reduced. When a metaloxide, which can be formed at a lower temperature than polycrystallinesilicon, is used, materials with low heat resistance can be used for awiring, an electrode, or a substrate below the semiconductor layer, sothat the range of choices of materials can be widened. For example, anextremely large glass substrate can be favorably used.

A metal oxide film with low carrier density is used as the semiconductorlayer. For example, the semiconductor layer is a metal oxide whosecarrier density is lower than or equal to 1×10¹⁷/cm³, preferably lowerthan or equal to 1×10¹⁵/cm³, further preferably lower than or equal to1×10¹³/cm³, still further preferably lower than or equal to 1×10¹¹/cm³,even further preferably lower than 1×10¹⁰/cm³, and higher than or equalto 1×10⁻⁹/cm³. Such a metal oxide is referred to as a highly purifiedintrinsic or substantially highly purified intrinsic metal oxide. Themetal oxide has a low impurity concentration and a low density of defectstates and can thus be referred to as a metal oxide having stablecharacteristics.

Note that, without limitation to those described above, a material withan appropriate composition may be used depending on requiredsemiconductor characteristics and electrical characteristics (e.g.,field-effect mobility and threshold voltage) of a transistor. To obtainthe required semiconductor characteristics of the transistor, it ispreferable that the carrier density, the impurity concentration, thedefect density, the atomic ratio between a metal element and oxygen, theinteratomic distance, the density, and the like of the semiconductorlayer be set to appropriate values.

When silicon or carbon that is one of elements belonging to Group 14 iscontained in the metal oxide contained in the semiconductor layer,oxygen vacancies are increased in the semiconductor layer, and thesemiconductor layer becomes n-type. Thus, the concentration of siliconor carbon (measured by secondary ion mass spectrometry) in thesemiconductor layer is lower than or equal to 2×10¹⁸ atoms/cm³,preferably lower than or equal to 2×10¹⁷ atoms/cm³.

Alkali metal and alkaline earth metal might generate carriers whenbonded to a metal oxide, in which case the off-state current of thetransistor might be increased. Therefore, the concentration of alkalimetal or alkaline earth metal of the semiconductor layer, which ismeasured by secondary ion mass spectrometry, is lower than or equal to1×10¹⁸ atoms/cm³, preferably lower than or equal to 2×10¹⁶ atoms/cm³.

When nitrogen is contained in the metal oxide contained in thesemiconductor layer, electrons serving as carriers are generated and thecarrier density increases, so that the semiconductor layer easilybecomes n-type. Thus, a transistor including a metal oxide that containsnitrogen is likely to be normally on. Hence, the concentration ofnitrogen in the semiconductor layer which is measured by secondary ionmass spectrometry is preferably lower than or equal to 5×10¹⁸ atoms/cm³.

The semiconductor layer may have a non-single-crystal structure, forexample. The non-single-crystal structure includes CAAC-OS (c-axisaligned crystalline oxide semiconductor, or c-axis aligneda-b-plane-anchored crystalline oxide semiconductor) including a c-axisaligned crystal, a polycrystalline structure, a microcrystallinestructure, or an amorphous structure, for example. Among thenon-single-crystal structures, an amorphous structure has the highestdensity of defect states, whereas CAAC-OS has the lowest density ofdefect states.

A metal oxide film having an amorphous structure has disordered atomicarrangement and no crystalline component, for example. Alternatively, anoxide film having an amorphous structure has, for example, an absolutelyamorphous structure and no crystal part.

Note that the semiconductor layer may be a mixed film including two ormore of the following: a region having an amorphous structure, a regionhaving a microcrystalline structure, a region having a polycrystallinestructure, a region of CAAC-OS, and a region having a single-crystalstructure. The mixed film has, for example, a single-layer structure ora stacked-layer structure including two or more of the above-describedregions in some cases.

<Composition of CAC-OS>

Described below is the composition of a cloud-aligned composite oxidesemiconductor (CAC-OS) applicable to a transistor disclosed in oneembodiment of the present invention.

In this specification and the like, a metal oxide means an oxide ofmetal in a broad sense. Metal oxides are classified into an oxideinsulator, an oxide conductor (including a transparent oxide conductor),an oxide semiconductor (also simply referred to as an OS), and the like.For example, a metal oxide used in an active layer of a transistor iscalled an oxide semiconductor in some cases. In other words, an OS FETis a transistor including a metal oxide or an oxide semiconductor.

In this specification, a metal oxide in which regions functioning as aconductor and regions functioning as a dielectric are mixed and whichfunctions as a semiconductor as a whole is defined as a CAC-OS or aCAC-metal oxide.

The CAC-OS has, for example, a composition in which elements included inan oxide semiconductor are unevenly distributed. Materials includingunevenly distributed elements each have a size of greater than or equalto 0.5 nm and less than or equal to 10 nm, preferably greater than orequal to 0.5 nm and less than or equal to 3 nm, or a similar size. Notethat in the following description of an oxide semiconductor, a state inwhich one or more elements are unevenly distributed and regionsincluding the element(s) are mixed is referred to as a mosaic pattern ora patch-like pattern. The region has a size of greater than or equal to0.5 nm and less than or equal to 10 nm, preferably greater than or equalto 0.5 nm and less than or equal to 3 nm, or a similar size.

The physical properties of a region including an unevenly distributedelement are determined by the properties of the element. For example, aregion including an unevenly distributed element which relatively tendsto serve as an insulator among elements included in a metal oxide servesas a dielectric region. In contrast, a region including an unevenlydistributed element which relatively tends to serve as a conductor amongelements included in a metal oxide serves as a conductive region. Amaterial in which conductive regions and dielectric regions are mixed toform a mosaic pattern serves as a semiconductor.

That is, a metal oxide in one embodiment of the present invention is akind of matrix composite or metal matrix composite, in which materialshaving different physical properties are mixed.

Note that an oxide semiconductor preferably contains at least indium. Inparticular, indium and zinc are preferably contained. In addition, anelement M (M is one or more of gallium, aluminum, silicon, boron,yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium,zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum,tungsten, magnesium, and the like) may be contained.

For example, of the CAC-OS, an In—Ga—Zn oxide with the CAC composition(such an In—Ga—Zn oxide may be particularly referred to as CAC-IGZO) hasa composition in which materials are separated into indium oxide(InO_(X1), where X1 is a real number greater than 0) or indium zincoxide (In_(X2)Zn_(Y2)O_(Z2), where X2, Y2, and Z2 are real numbersgreater than 0), and gallium oxide (GaO_(X3), where X3 is a real numbergreater than 0) or gallium zinc oxide (Ga_(X4)Zn_(Y4)O_(Z4), where X4,Y4, and Z4 are real numbers greater than 0), and a mosaic pattern isformed. Then, InO_(X1) or In_(X2)Zn_(Y2)O_(Z2) forming the mosaicpattern is evenly distributed in the film. This composition is alsoreferred to as a cloud-like composition.

That is, the CAC-OS is a composite oxide semiconductor with acomposition in which a region including GaO_(X3) as a main component anda region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main componentare mixed. Note that in this specification, for example, when the atomicratio of In to an element M in a first region is greater than the atomicratio of In to an element M in a second region, the first region hashigher In concentration than the second region.

Note that a compound including In, Ga, Zn, and O is also known as IGZO.Typical examples of IGZO include a crystalline compound represented byInGaO₃(ZnO)_(m1) (m1 is a natural number) and a crystalline compoundrepresented by In_((1+x0))Ga_((1−x0))O₃(ZnO)_(m0) (−1≤x0≤1; m0 is agiven number).

The above crystalline compounds have a single crystal structure, apolycrystalline structure, or a CAAC structure. Note that the CAACstructure is a crystal structure in which a plurality of IGZOnanocrystals have c-axis alignment and are connected in the a-b planedirection without alignment.

On the other hand, the CAC-OS relates to the material composition of anoxide semiconductor. In a material composition of a CAC-OS including In,Ga, Zn, and O, nanoparticle regions including Ga as a main component areobserved in part of the CAC-OS and nanoparticle regions including In asa main component are observed in part thereof. These nanoparticleregions are randomly dispersed to form a mosaic pattern. Therefore, thecrystal structure is a secondary element for the CAC-OS.

Note that in the CAC-OS, a stacked-layer structure including two or morefilms with different compositions is not included. For example, atwo-layer structure of a film including In as a main component and afilm including Ga as a main component is not included.

A boundary between the region including GaO_(X3) as a main component andthe region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent is not clearly observed in some cases.

In the case where one or more of aluminum, silicon, boron, yttrium,copper, vanadium, beryllium, titanium, iron, nickel, germanium,zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum,tungsten, magnesium, and the like are contained instead of gallium in aCAC-OS, nanoparticle regions including the selected element(s) as a maincomponent(s) are observed in part of the CAC-OS and nanoparticle regionsincluding In as a main component are observed in part thereof, and thesenanoparticle regions are randomly dispersed to form a mosaic pattern inthe CAC-OS.

<Analysis of CAC-OS>

Next, measurement results of an oxide semiconductor over a substrate bya variety of methods are described.

<<Structure of Samples and Formation Method Thereof>>

Nine samples of one embodiment of the present invention are describedbelow. The samples are formed at different substrate temperatures andwith different ratios of an oxygen gas flow rate in formation of theoxide semiconductor. Note that each sample includes a substrate and anoxide semiconductor over the substrate.

A method for forming the samples is described.

A glass substrate is used as the substrate. Over the glass substrate, a100-nm-thick In—Ga—Zn oxide is formed as an oxide semiconductor with asputtering apparatus. The formation conditions are as follows: thepressure in a chamber is 0.6 Pa, and an oxide target (with an atomicratio of In:Ga:Zn=4:2:4.1) is used as a target. The oxide targetprovided in the sputtering apparatus is supplied with an AC power of2500 W.

As for the conditions in the formation of the oxide of the nine samples,the substrate temperature is set to a temperature that is not increasedby intentional heating (hereinafter such a temperature is also referredto as room temperature or R.T.), to 130° C., and to 170° C. The ratio ofa flow rate of an oxygen gas to a flow rate of a mixed gas of Ar andoxygen (also referred to as an oxygen gas flow rate ratio) is set to10%, 30%, and 100%.

<<Analysis by X-Ray Diffraction>>

In this section, results of X-ray diffraction (XRD) measurementperformed on the nine samples are described. As an XRD apparatus, D8ADVANCE manufactured by Bruker AXS is used. The conditions are asfollows: scanning is performed by an out-of-plane method at θ/2θ, thescanning range is 15 deg. to 50 deg., the step width is 0.02 deg., andthe scanning speed is 3.0 deg./min.

FIG. 27 shows XRD spectra measured by an out-of-plane method. In FIG.27, the top row shows the measurement results of the samples formed at asubstrate temperature of 170° C.; the middle row shows the measurementresults of the samples formed at a substrate temperature of 130° C.; andthe bottom row shows the measurement results of the samples formed at asubstrate temperature of R.T. The left column shows the measurementresults of the samples formed with an oxygen gas flow rate ratio of 10%;the middle column shows the measurement results of the samples formedwith an oxygen gas flow rate ratio of 30%; and the right column showsthe measurement results of the samples formed with an oxygen gas flowrate ratio of 100%.

In the XRD spectra shown in FIG. 27, the higher the substratetemperature at the time of formation is or the higher the oxygen gasflow rate ratio at the time of formation is, the higher the intensity ofthe peak at around 2θ=31° is. Note that it is found that the peak ataround 2θ=31° is derived from a crystalline IGZO compound whose c-axesare aligned in a direction substantially perpendicular to a formationsurface or a top surface of the crystalline IGZO compound (such acompound is also referred to as c-axis aligned crystalline (CAAC) IGZO).

As shown in the XRD spectra in FIG. 27, as the substrate temperature atthe time of formation is lower or the oxygen gas flow rate ratio at thetime of formation is lower, a peak becomes less clear. Accordingly, itis found that there are no alignment in the a-b plane direction andc-axis alignment in the measured areas of the samples that are formed ata lower substrate temperature or with a lower oxygen gas flow rateratio.

<<Analysis with Electron Microscope>>

This section describes the observation and analysis results of thesamples formed at a substrate temperature of R.T. and with an oxygen gasflow rate ratio of 10% with a high-angle annular dark-field scanningtransmission electron microscope (HAADF-STEM). An image obtained with anHAADF-STEM is also referred to as a TEM image.

Described are the results of image analysis of plan-view images andcross-sectional images obtained with an HAADF-STEM (also referred to asplan-view TEM images and cross-sectional TEM images, respectively). TheTEM images are observed with a spherical aberration corrector function.The HAADF-STEM images are obtained using an atomic resolution analyticalelectron microscope JEM-ARM200F manufactured by JEOL Ltd. under thefollowing conditions: the acceleration voltage is 200 kV, andirradiation with an electron beam with a diameter of approximately 0.1nm is performed.

FIG. 28A is a plan-view TEM image of the sample formed at a substratetemperature of R.T. and with an oxygen gas flow rate ratio of 10%. FIG.28B is a cross-sectional TEM image of the sample formed at a substratetemperature of R.T. and with an oxygen gas flow rate ratio of 10%.

<<Analysis of Electron Diffraction Patterns>>

This section describes electron diffraction patterns obtained byirradiation of the sample formed at a substrate temperature of R.T. andan oxygen gas flow rate ratio of 10% with an electron beam with a probediameter of 1 nm (also referred to as a nanobeam).

Electron diffraction patterns of points indicated by black dots a1, a2,a3, a4, and a5 in the plan-view TEM image in FIG. 28A of the sampleformed at a substrate temperature of R.T. and an oxygen gas flow rateratio of 10% are observed. Note that the electron diffraction patternsare observed while electron beam irradiation is performed at a constantrate for 35 seconds. FIGS. 28C, 28D, 28E, 28F, and 28G show the resultsof the points indicated by the black dots a1, a2, a3, a4, and a5,respectively.

In FIGS. 28C, 28D, 28E, 28F, and 28G, regions with high luminance in acircular (ring) pattern can be shown. Furthermore, a plurality of spotscan be shown in a ring-like shape.

Electron diffraction patterns of points indicated by black dots b1, b2,b3, b4, and b5 in the cross-sectional TEM image in FIG. 28B of thesample formed at a substrate temperature of R.T. and an oxygen gas flowrate ratio of 10% are observed. FIGS. 28H, 28I, 28J, 28K, and 28L showthe results of the points indicated by the black dots b1, b2, b3, b4,and b5, respectively.

In FIGS. 28H, 28I, 28J, 28K, and 28L, regions with high luminance in aring pattern can be shown. Furthermore, a plurality of spots can beshown in a ring-like shape.

For example, when an electron beam with a probe diameter of 300 nm isincident on a CAAC-OS including an InGaZnO₄ crystal in a directionparallel to the sample surface, a diffraction pattern including a spotderived from the (009) plane of the InGaZnO₄ crystal is obtained. Thatis, the CAAC-OS has c-axis alignment and the c-axes are aligned in thedirection substantially perpendicular to the formation surface or thetop surface of the CAAC-OS. Meanwhile, a ring-like diffraction patternis shown when an electron beam with a probe diameter of 300 nm isincident on the same sample in a direction perpendicular to the samplesurface. That is, it is found that the CAAC-OS has neither a-axisalignment nor b-axis alignment.

Furthermore, a diffraction pattern like a halo pattern is observed whenan oxide semiconductor including a nanocrystal (a nanocrystalline oxidesemiconductor (nc-OS)) is subjected to electron diffraction using anelectron beam with a large probe diameter (e.g., 50 nm or larger).Meanwhile, bright spots are shown in a nanobeam electron diffractionpattern of the nc-OS obtained using an electron beam with a small probediameter (e.g., smaller than 50 nm). Furthermore, in a nanobeam electrondiffraction pattern of the nc-OS, regions with high luminance in acircular (ring) pattern are shown in some cases. Also in a nanobeamelectron diffraction pattern of the nc-OS, a plurality of bright spotsare shown in a ring-like shape in some cases.

The electron diffraction pattern of the sample formed at a substratetemperature of R.T. and with an oxygen gas flow rate ratio of 10% hasregions with high luminance in a ring pattern and a plurality of brightspots appear in the ring-like pattern. Accordingly, the sample formed ata substrate temperature of R.T. and with an oxygen gas flow rate ratioof 10% exhibits an electron diffraction pattern similar to that of thenc-OS and does not show alignment in the plane direction and thecross-sectional direction.

According to what is described above, an oxide semiconductor formed at alow substrate temperature or with a low oxygen gas flow rate ratio islikely to have characteristics distinctly different from those of anoxide semiconductor film having an amorphous structure and an oxidesemiconductor film having a single crystal structure.

<<Elementary Analysis>>

This section describes the analysis results of elements included in thesample formed at a substrate temperature of R.T. and with an oxygen gasflow rate ratio of 10%. For the analysis, by energy dispersive X-rayspectroscopy (EDX), EDX mapping images are obtained. An energydispersive X-ray spectrometer AnalysisStation JED-2300T manufactured byJEOL Ltd. is used as an elementary analysis apparatus in the EDXmeasurement. A Si drift detector is used to detect an X-ray emitted fromthe sample.

In the EDX measurement, an EDX spectrum of a point is obtained in such amanner that electron beam irradiation is performed on the point in adetection target region of a sample, and the energy of characteristicX-ray of the sample generated by the irradiation and its frequency aremeasured. In this embodiment, peaks of an EDX spectrum of the point areattributed to electron transition to the L shell in an In atom, electrontransition to the K shell in a Ga atom, and electron transition to the Kshell in a Zn atom and the K shell in an O atom, and the proportions ofthe atoms in the point are calculated. An EDX mapping image indicatingdistributions of proportions of atoms can be obtained through theprocess in an analysis target region of a sample.

FIGS. 29A to 29C show EDX mapping images in a cross section of thesample formed at a substrate temperature of R.T. and with an oxygen gasflow rate ratio of 10%. FIG. 29A shows an EDX mapping image of Ga atoms.The proportion of the Ga atoms in all the atoms is 1.18 atomic % to18.64 atomic %. FIG. 29B shows an EDX mapping image of In atoms. Theproportion of the In atoms in all the atoms is 9.28 atomic % to 33.74atomic %. FIG. 29C shows an EDX mapping image of Zn atoms. Theproportion of the Zn atoms in all the atoms is 6.69 atomic % to 24.99atomic %. FIGS. 29A to 29C show the same region in the cross section ofthe sample formed at a substrate temperature of R.T. and with an oxygengas flow rate ratio of 10%. In the EDX mapping images, the proportion ofan element is indicated by gray scale: the more measured atoms exist ina region, the brighter the region is; the less measured atoms exist in aregion, the darker the region is. The magnification of the EDX mappingimages in FIGS. 29A to 29C is 7200000 times.

The EDX mapping images in FIGS. 29A to 29C show relative distribution ofbrightness indicating that each element has a distribution in the sampleformed at a substrate temperature of R.T. and with an oxygen gas flowrate ratio of 10%. Areas surrounded by solid lines and areas surroundedby dashed lines in FIGS. 29A to 29C are examined.

In FIG. 29A, a relatively dark region occupies a large area in the areasurrounded by the solid line, while a relatively bright region occupiesa large area in the area surrounded by the dashed line. In FIG. 29B, arelatively bright region occupies a large area in the area surrounded bythe solid line, while a relatively dark region occupies a large area inthe area surrounded by the dashed line.

That is, the areas surrounded by the solid lines are regions including arelatively large number of In atoms and the areas surrounded by thedashed lines are regions including a relatively small number of Inatoms. In FIG. 29C, the right portion of the area surrounded by thesolid line is relatively bright and the left portion thereof isrelatively dark. Thus, the area surrounded by the solid line is a regionincluding In_(X2)Zn_(Y2)O_(Z2), InO_(X1), or the like as a maincomponent.

The area surrounded by the solid line is a region including a relativelysmall number of Ga atoms and the area surrounded by the dashed line is aregion including a relatively large number of Ga atoms. In FIG. 29C, theupper left portion of the area surrounded by the dashed line isrelatively bright and the lower right portion thereof is relativelydark. Thus, the area surrounded by the dashed line is a region includingGaO_(X3), Ga_(X4)Zn_(Y4)O_(Z4), or the like as a main component.

Furthermore, as shown in FIGS. 29A to 29C, the In atoms are relativelymore uniformly distributed than the Ga atoms, and regions includingInO_(X1) as a main component are seemingly joined to each other througha region including In_(X2)Zn_(Y2)O_(Z2) as a main component. Thus, theregions including In_(X2)Zn_(Y2)O_(Z2) and InO_(X1) as main componentsextend like a cloud.

An In—Ga—Zn oxide having a composition in which the regions includingGaO_(X3) or the like as a main component and the regions includingIn_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component are unevenlydistributed and mixed can be referred to as a CAC-OS.

The crystal structure of the CAC-OS includes an nc structure. In anelectron diffraction pattern of the CAC-OS with the nc structure,several or more bright spots appear in addition to bright sports derivedfrom IGZO including a single crystal, a polycrystal, or a CAAC.Alternatively, the crystal structure is defined as having high luminanceregions appearing in a ring pattern in addition to the several or morebright spots.

As shown in FIGS. 29A to 29C, each of the regions including GaO_(X3) orthe like as a main component and the regions includingIn_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component has a size ofgreater than or equal to 0.5 nm and less than or equal to 10 nm, orgreater than or equal to 1 nm and less than or equal to 3 nm. Note thatit is preferable that a diameter of a region including each element as amain component be greater than or equal to 1 nm and less than or equalto 2 nm in the EDX mapping images.

As described above, the CAC-OS has a structure different from that of anIGZO compound in which metal elements are evenly distributed, and hascharacteristics different from those of the IGZO compound. That is, inthe CAC-OS, regions including GaO_(X3) or the like as a main componentand regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent are separated to form a mosaic pattern.

The conductivity of a region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1)as a main component is higher than that of a region including GaO_(X3)or the like as a main component. In other words, when carriers flowthrough regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent, the conductivity of an oxide semiconductor is exhibited.Accordingly, when regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) asa main component are distributed in an oxide semiconductor like a cloud,a high field-effect mobility (μ) can be achieved.

In contrast, the insulating property of a region including GaO_(X3) orthe like as a main component is higher than that of a region includingIn_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component. In other words,when regions including GaO_(X3) or the like as a main component aredistributed in an oxide semiconductor, leakage current can be suppressedand favorable switching operation can be achieved.

Accordingly, when a CAC-OS is used for a semiconductor element, theinsulating property derived from GaO_(X3) or the like and theconductivity derived from In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) complementeach other, whereby a high on-state current (I_(on)) and a highfield-effect mobility (μ) can be achieved.

A semiconductor element including a CAC-OS has high reliability. Thus,the CAC-OS is suitably used in a variety of semiconductor devicestypified by a display.

Since a transistor including a CAC-OS in a semiconductor layer has highfield-effect mobility and high driving capability, the use of thetransistor in a driver circuit, a typical example of which is a gateline driver circuit that generates a gate signal, allows a displaydevice to have a narrow bezel. Furthermore, the use of the transistor ina signal line driver circuit (particularly in a demultiplexer connectedto an output terminal of a shift register included in a signal linedriver circuit) that is included in a display device and supplies asignal from a signal line can reduce the number of wirings connected tothe display device.

Furthermore, the transistor including a CAC-OS in the semiconductorlayer does not need a laser crystallization step like a transistorincluding low-temperature polysilicon. Thus, the manufacturing cost of adisplay device can be reduced, even when the display device is formedusing a large substrate. In addition, when the transistor including aCAC-OS in the semiconductor layer is used for a driver circuit and adisplay portion in a large display device having high resolution such asultra high definition (“4K resolution”, “4K2K”, and “4K”) or super highdefinition (“8K resolution”, “8K4K”, and “8K”), writing can be performedin a short time, and display defects can be reduced, which ispreferable.

Alternatively, silicon may be used as a semiconductor in which a channelof a transistor is formed. Although amorphous silicon may be used assilicon, silicon having crystallinity is particularly preferable. Forexample, microcrystalline silicon, polycrystalline silicon, singlecrystal silicon, or the like is preferably used. In particular,polycrystalline silicon can be formed at a lower temperature than singlecrystal silicon and has a higher field effect mobility and higherreliability than amorphous silicon.

The bottom-gate transistor described in this embodiment is preferablebecause the number of manufacturing steps can be reduced. When amorphoussilicon, which can be formed at a lower temperature than polycrystallinesilicon, is used for the semiconductor layer, materials with low heatresistance can be used for a wiring, an electrode, or a substrate belowthe semiconductor layer, resulting in wider choice of materials. Forexample, an extremely large glass substrate can be favorably used.Meanwhile, the top-gate transistor is preferable because an impurityregion is easily formed in a self-aligned manner and variation incharacteristics can be reduced. The top-gate transistor is particularlypreferable when polycrystalline silicon, single-crystal silicon, or thelike is employed.

At least part of this embodiment can be implemented in combination withany of the other embodiments described in this specification asappropriate.

REFERENCE NUMERALS

ACF1: conductive material, ADD: wiring, AF1: alignment film, AF2:alignment film, ANO: wiring, BM: light-blocking film, C11: capacitor,C12: capacitor, CF1: coloring film, COM: wiring, COM-Rx: wiring, COM-Tx:wiring, CSCOM: wiring, CTRL: wiring, G1: scan line, G2: scan line, GVSS:wiring, KB1: structure body, L1: visible light, L2: light, ND1: wiring,ND2: wiring, ND3: wiring, R1: arrow, S1: signal line, S2: signal line,SD1: driver circuit, SD2: driver circuit, SW1: switch, SW2: switch, V11:data, V12: data, VCOM1: wiring, VCOM2: conductive layer, 10: displaydevice, 11: substrate, 12: substrate, 13: FPC, 14: conductive layer, 20:liquid crystal element, 21: conductive layer, 21 a: conductive layer, 21b: conductive layer, 22: conductive layer, 22 a: conductive layer, 22 b:conductive layer, 22 c: conductive layer, 23: liquid crystal, 24:insulating layer, 31: coloring film, 61: gate driver, 61 a: decoder, 61b: selection circuit, 61 c: shift register, 61 d: switch, 61 e: switch,61 f: switch, 61 g: buffer, 61 h: switch, 62: receiver circuit, 63:touch sensor, 64: pixel, 64 a: selection transistor, 64 b: capacitor, 64c: liquid crystal display element, 64 d: contact, 64 e: contact, 64 f:common electrode, 64 g: contact, 64 h: wiring, 65: scan line, 66: signalline, 67: capacitor, 68: pixel electrode, 200: liquid crystal displaydevice, 201: display portion, 202: gate line driver circuit, 203: pixel,231: display region, 305 a: connection portion, 307 a: liquid crystalelement, 307 b: liquid crystal element, 311: substrate, 312: insulatinglayer, 313: insulating layer, 315: insulating layer, 317: insulatinglayer, 319: insulating layer, 331: conductive layer, 333: conductivelayer, 335: conductive layer, 341: coloring film, 343: light-blockingfilm, 345: insulating layer, 347: spacer, 349: liquid crystal, 351:conductive layer, 352: conductive layer, 352 a: wiring, 353: insulatinglayer, 361: substrate, 365: adhesive layer, 367: connector, 368: IC,369: FPC, 370 a: transistor, 372: polysilicon film, 373: conductivelayer, 374 a: conductive layer, 374 b: conductive layer, 380 a:transistor, 501B: insulating film, 501C: insulating film, 504:conductive layer, 505: bonding layer, 506: insulating film, 508:semiconductor film, 511B: conductive layer, 512A: conductive layer,512B: conductive layer, 516: insulating film, 518: insulating film,518A: insulating film, 518A1: insulating film, 518A2: insulating film,518B: insulating film, 519B: terminal, 520: functional layer, 521:insulating film, 521A: insulating film, 521B: insulating film, 521C:insulating film, 522: connection portion, 524: conductive layer, 528:insulating film, 530: pixel circuit, 550: display element, 551:electrode, 552: electrode, 553: layer containing a light-emittingmaterial, 560: optical element, 560A: region, 560B: region, 560C:region, 565: covering film, 570: substrate, 580: lens, 591A: opening,592B: opening, 700: display device, 700B: display device, 702: pixel,703: pixel, 705: sealing material, 720: functional layer, 750: displayelement, 751: first electrode, 751A: conductive layer, 751B: reflectivefilm, 751C: conductive layer, 751H: region, 752: second electrode, 753:layer containing a liquid crystal material, 770: substrate, 770D:functional film, 770P: functional film, 770PA: functional film, 770PB:functional film, 771: insulating film, 771A: insulating film, 771B:insulating film, 5200B: data processing device, 5210: arithmetic device,5220: input/output device, 5230: display portion, 5240: input portion,5250: sensor portion, 5290: communication portion

This application is based on Japanese Patent Application Serial No.2016-207008 filed with Japan Patent Office on Oct. 21, 2016, the entirecontents of which are hereby incorporated by reference.

The invention claimed is:
 1. A display device comprising: a gate driver;g wirings; a plurality of touch sensors arranged in a matrix with m rowsand k columns; m wirings; and a plurality of first touch wirings, eachof the plurality of first touch wirings provided between two of the gwirings, wherein the m wirings are respectively connected to theplurality of touch sensors in an n-th column of the k columns and thefirst to m-th rows that are directly adjacent, wherein the gate driveris configured to supply a first scan signal to the g wirings at a samefirst timing, wherein the plurality of touch sensors in differentpositions are configured to sense a plurality of touches at a samesecond timing, wherein g, m, and k are each a natural number of 2 ormore, and n is a natural number of 1 or more, and wherein the pluralityof touch sensors are spaced apart from each other.
 2. The display deviceaccording to claim 1, further comprising a pixel, wherein the gatedriver is configured to supply a second scan signal to the plurality offirst touch wirings, wherein the m wirings electrically connected to areceiver circuit intersect with the plurality of first touch wirings,wherein the pixel comprises a first display element, and wherein thefirst display element is a transmissive liquid crystal element.
 3. Thedisplay device according to claim 1, further comprising a pixel, whereinthe pixel comprises a first display element, and wherein the firstdisplay element is a reflective liquid crystal element.
 4. The displaydevice according to claim 3, wherein the pixel comprises the firstdisplay element and a second display element, wherein the first displayelement is configured to reflect visible light, and wherein the seconddisplay element is configured to emit visible light.
 5. The displaydevice according to claim 4, wherein the second display element is alight-emitting element.
 6. The display device according to claim 4,wherein an image is displayed with one or both of first light reflectedby the first display element and second light emitted by the seconddisplay element.
 7. The display device according to claim 1, furthercomprising: a transistor, wherein the transistor comprises polysiliconin a semiconductor layer, and wherein the gate driver further includes adecoder, a plurality of selection circuits, and a plurality of buffers.8. The display device according to claim 1, further comprising: atransistor, wherein the transistor comprises a metal oxide in asemiconductor layer, and wherein the m wirings electrically connected toa receiver circuit overlap with the g wirings and the plurality of touchsensors.
 9. A display device comprising: a receiver circuit, a displayregion; and a gate driver, wherein the display region comprises a pixel,a plurality of touch sensors arranged in a matrix with m rows and kcolumns, g wirings, and m wirings, wherein the g wirings are providedfor touch sensors of the plurality of touch sensors in a plurality ofcolumns and a single row, wherein the m wirings are respectivelyconnected to the plurality of touch sensors in an n-th column of the kcolumns and the first to m-th rows that are directly adjacent, whereinthe gate driver is configured to supply a first scan signal to aplurality of scan lines, wherein the m wirings are electricallyconnected to the receiver circuit, wherein the gate driver is configuredto supply a second scan signal for sensing a touch to the g wirings, andwherein g, m, and k are each a natural number of 2 or more, and n is anatural number of 1 or more.
 10. The display device according to claim9, wherein the plurality of touch sensors are spaced apart from eachother, wherein the pixel comprises a first display element, and whereinthe first display element is a transmissive liquid crystal element. 11.The display device according to claim 10, wherein touch sensors adjacentto each other in a row direction are spaced a part from each other. 12.The display device according to claim 9, wherein the m wirings intersectwith the g wirings, wherein the pixel comprises a first display element,and wherein the first display element is a reflective liquid crystalelement.
 13. The display device according to claim 12, wherein the pixelcomprises the first display element and a second display element,wherein the first display element is configured to reflect visiblelight, and wherein the second display element is configured to emitvisible light.
 14. The display device according to claim 13, wherein thesecond display element is a light-emitting element.
 15. The displaydevice according to claim 13, wherein an image is displayed with one orboth of first light reflected by the first display element and secondlight emitted by the second display element.
 16. The display deviceaccording to claim 13, further comprising: a transistor in the pixel,wherein the transistor comprises polysilicon in a semiconductor layer,and wherein the gate driver further includes a decoder, a plurality ofselection circuits, and a plurality of buffers.
 17. The display deviceaccording to claim 13, further comprising: a transistor in the pixel,wherein the transistor comprises a metal oxide in a semiconductor layer,and wherein the plurality of scan lines overlap with the plurality oftouch sensors and the m wirings.
 18. The display device according toclaim 1, wherein touch sensors adjacent to each other in a row directionare spaced a part from each other.